TOD discussion

[Nazrat]

http://forum.australia4wd.com/lofiversion/index.php/t1153.html

-Tad

[bobmumgaard]

The guys on the link above and it's links have got the TOD system pinned down and solved.
If our system is the same as theirs (and it must be pretty close, same manufacturer, overal design, and basic operation) then the TOD brain sends a 50Hz PWM (pulse width modulation) signal to the transfer case solenoid with a duty cycle between 0% and 88%.

(0% being no torque to front and 88% being 50/50 split)

Aside for those not electrical engineering prone:
PWM sends a square wave to the load, this square wave has a peak voltage of about ~13.6V(in our case at least). By altering the width of the square wave you can change the effective voltage the load sees. So with an 88% duty cycle, the square wave occurs over 88% of the period and the average voltage to the load is about 12V. So if we wanted the load to see 7.2 V (this would be about 30% torque to the front) we would send a duty cycle of around 53%.
The advantages of PWM make it very common in automotive apllications, these advantages include a resistance to electrical noise, ablity to integrate digital and analoge components and a lower strain on electrical components (the current in PWM only flows for a fraction of an analoge only system). Infact many sensors, including most speed sensors use PWM.


Onward with the TOD side
This means we can alter the amount of transfer case lockup by altering the PWM signal the solenoid sees.

So heres a proposed idea:
If we want to have 4hi, 2hi, or anything in between (say 30% torque to the front) we could disconnect the TOD ecu from the solenoid (and connect the TOD ecu to a false load, say a 5? ohm resistor) and connect the solenoid to a PWM controler that we can vary. This PWM would be variable from 0% to 88%. (0V to 12V rms) this way we could dial in the amount of transfer case lock-up from 0 (2hi) to 50/50 (4hi).

The implications for those that want to full control over their TOD are huge. You could have a dial that selects the amount of torque to the front much like a rally car would. And the signal would be the same configuration the TOD auto mode sends, so no adverse affects. And if you wanted TOD auto mode you would reconnect the TOD ecu to the solenoid (with a relay) this would set the system up to operate as usual.

Modification could be made from there:
You could directly alter the TOD display lights with a series of relays in conjuction with the PWM controler so the display would display the front torgue correctly. You could aslo use a clever set of relays to set the sysem up so the TOD ecu automatically regains control over the transfer case in certain situations like 4 low or when the abs activates. Though i have not thought these all the way through yet they remain tantalyzing possiblities.

And, theorectically, the system could be done even simpler. The soleniod might not NEED to see a PWM signal to operate, you could simply alter the voltage it sees with a poteniometer instead of a PWM controller. Though this idea is alittle hairy because the potential for excessive wear and adverse affects because the signal the solenoid receives is not of the same form as it is design to use. I would have to do some extensive tests with the transfer case outside the vehicle to be sure how this could work.

So it looks like this winter I will be driving around in the snow with no passenger seat and a multimeter and oscillosope hooked to the TOD ecu to soleniod wire. Hopefully this research will confirm what the aussie and spanish Terracan drivers have discovered. From there it will be a matter of constructing the right circuit and we could have a viable torque split selector.


Anyway, if you read this and think I'm wrong, right or a moron, shoot back your ideas. With alittle brainstorming I think we could come up with a pretty nifty, inexpensive and reversible solution for those that want complete control over their transfer case.

[Joe_Black]

The Isuzu rally teams had an electronically selectable TOD ratio in their 5-speed VehiCROSSes, so it's basically knowing what/how to connect. From what I was able to read about the competition set-up indicated simplicity and plug-n-play reversibility to stock.

[Ldub]

Bob M,
YOU DA MAN...wish I had the tech. abilities reqd. to figure something this complex out in the first place. Seriuosly, your aside for the non elec. eng. prone was too deep for me.
However, if you get a handle on this thing & produce a few "plug & play" units (harness, controller, DETAILED instructions, etc.) You can count me in as your first customer.

Hope ya get it to work, Ldub

[mbeach]

I couldn't open the Terracan links, but I have been suspecting the same thing (PWM signal) for a couple of weeks.

I have plenty of snow for practice, what wire(s) should I monitor?
I think that a few inputs would be in order (front axle, rear axle, ABS, 4Lo) to the TOD ecu.
I'd definately monitor the TOD to clutch solenoid as well.

I figure that this weekend I could get started checking voltages and frequencies under various conditions. It will be difficult to catch a 70/30 or an 85/15 condition however. It seems that TOD is all-or-nothing on ice and snow.

I'll think about a nice spreadsheet for gathering all of this data.

If we get the right information together, I have an extensive inventory of tools and parts to make this happen.
Heck, if it works I might not sell the VX after all.

[mbeach]

I was discussing this with my lead tech (super genius).

We can make this happen, BUT:
I need a TOD computer. They pop up on eBay all the time, except for today. I will pay up to $100 for one, I cannot use of of mine right now (too much ice on the road still).

We were thinking about catching the signal INSIDE of the TOD computer, before it hits the amplifier section. This should eliminate the need for a dummy load. We can make a PWM generator with a timer (555?). By altering the control voltage into the timer, we should be able to modify the square wave output. This means a KNOB, with infinite variability or presets (whichever you want).

HELP ME FIND A COMPUTER!!!

[bobmumgaard]

mbeach-
I imagine you have the snow up there to try this, I fortunatly haven't got the white stuff down here NE yet.

If you want to monitor what the TOD ecu is doing I think monitoring these wires would be the most important:

1.
TOD to Solenoid - On a 2000 it is the light blue wire that exits the TOD ecu from pin 4
If you hook a multimeter to this wire and monitor voltage it should hover around 0-1V most of the time and jump when the TOD dislpay shows power to the front wheels. An ocsiloscope would confirm if this is indeed a PWM signal.

2.
Front and Rear vehicle speed sensors- On a 2000 TOD ECU the front is pin 24 (green/white or grey/white), the rear is pin 23 (green/yellow or grey/yellow) and the reference for these sensors is pin 15 (green or grey)
The TOD ecu's logic probably looks at a differential between these two sensors and then decides how much torque split to enact. We could probably gain alot of insight on the function of the ecu by doing the same thing. I assume these two are probably PWM signals as well. If you use an oscilloscope with two channels of imput you can see this PWM differential occur when the rears slip.

If you want to look at the circuit diagrams yourself you can use Tone's maintaintence cd (if you don't have one just e-mail him or post and I'm sure he'll hook you up) The most useful pages are:

Driveline/axle > Driveline control (TOD) > Basic diagnostics flow chart > Checking failed pin > Connector pin assignment
and
Body and acceserories > Wiring diagram > circuit diagram 19 (the second 19)

I agree, at this stage a spreadsheet would be very helpful here, the way I'd set it up is with columns for this data:

Front speed sensor duty cycle
Rear speed sensor duty cycle
TOD-solenoid duty cycle
TOD-solenoid rms Voltage
What the solenoid is doing (0 front, 50/50 etc.)

Alright, so after we get this information together (hopefully it will confirm what the Terracan guys have discovered) it is a matter of making the modifications

I talked to a few of my EE collegues and they all agreed that substituting our own controlled PWM signal to the clutch instead of the ECU's signal would be the best route. This could certainly be done with a 555 like your tech said and it would be fairly inexpensive. Though I personally don't have the indepth know-how to build the actual circuit, but I know people that do, and you sound like you might have the knowlege and tools.

After thinking about the actual mechanics of modifying this system I think we have three basic options:

1. Modify the signals coming into the TOD ecu
This basically tricks the TOD ecu into thinking the car is doing one thing, and we get the desired result from the TOD ecu outputs. So if we modify the front or rear speed sensor signals before the ecu, then the ecu thinks there is slipping and we get lock-up. The trooper guys have kinda done this by cutting the front sensor wires. Then the ecu sends power to the front axle, but also throws a code. This method would produce the correct dash display. Though it scares me because if something goes wrong the TOD ecu would get fried....$$$

2. Modify the action inside the TOD ecu
I think this is the approach you and your tech are talking about. It would be the most elegant because it would all be contained inside the existing black box. If you can score an extra TOD ecu it could be taken apart and investigated, reprogramed almost. However, this approach would be hard to duplicate for the electronically timid among the VX community. Though it seems to be the most technically interesting.

3. Modify the TOD ecu's outputs
This would consist of modifying the signal from the TOD ecu to the clutch like I mentioned before. It is not the most elegant because it wont display correctly on the dash display but it would be the least risky and easiest to duplicate. The risk is minimized because you couldn't hurt the ecu (since the modification is after the ecu, you would need a dummy load though), and the soleniod is probably robust enough to withstand any minor malfunction we casue. The electronic circuits could be contained in a project box that would require cutting only the wire going from the TOD ecu to the solenoid. This makes it easy to install and produce for members on this board (might as well spread the wealth ehhh), you would have to cut one wire, install the knob, hook up power and ground and you'd be set. I think this approach is the one I'll persue.

Well thats my take on the whole deal right now, throw back your opinions on it and we'll keep brainstorming, this shouldn't be that hard. Plus, once the research is done and the modification tested there are plenty of guys on this board that could benefit from the knowlege obtained.

[mbeach]

My initial idea was option 1. I liked the fact that the display would be correct. However, once the vehicle were stopped, the TOD would be thrown into confusion. So I abandoned it.

Option 2 is the most elegant, yet it is not reversable (easily), removable, or easily installed. I'm going to try to veer from this, but we'll see. My goal is to have a correct dash display, and 5 modes of operation: Auto, 2wd, 15, 30, 4hi. All selectable with a knob. I think that by keeping it simple (5 modes, or outputs rather than infinite) I can make the display work as well.

I would need to:
a) turn off the AUTO display when the knob is switched to any other position.
b) turn on the appropriate lights with each mode.
c) default to AUTO mode whenever 4Lo is activated -or maybe not. 2Lo is an interesting option, if it's even possible.

I guess that I'm looking at option 2.5. I want to be "inside" the TOD computer for the display benefits, but I want it to be accessable and easy for a novice to hook up.

I pick up a better (portable) scope this week. This weekend I'm going to pull the harness(s) off of the TOD computer and make extensions (to minimize my crawling under the seat) that I can easily tap in to. I have the workshop CD, I'll be looking it over tonight. I think that I have a few spare connectors around the shop.

[VehiGAZ]

I really appreciate this conversation, guys!

I want only one thing - to have a switch to flip to go into 50%/50% (4WD Hi) mode, which would be best on snowy roads when going into 4WD Low is overkill, while leaving it in Auto ToD mode means it is CONSTNATLY (and annoyingly) engaging and disengaging the front wheels.

I figure I can use a light-up switch to indicate that it's in the forced 4WD Hi mode. That means I should go with option 3, but without the multi-position selector.

So circuit-wise, my switch would be put a dummy load on the output to the ToD, correct? Any advice on how exactly to wire it, and what to put on the "alternate" circuit?

Lastly, I may have that extra ToD ECU you are looking for, mbeach. I will PM you.

[VehiGAZ]

mbeach, your PM box is full. I sent you an e-mail to your yahoo address instead.

[mbeach]

I cleaned out my PM box, please re-send your message -I have been without home internet for a few months :eek: thanks to a bum antenna for my wireless provider. I can't check webmail at work -I could use my phone but it takes forever.

I sat down with schematics and diagrams from the workshop CD last night. After about an hour, I think that I may have worked out a fair solution. One that will settle my desires as well as be easily installed and removed by anyone with fingers. I'm also looking at a 4hi only option as well (VehiGaz).

Just for kicks I looked up the TOD patent, just to see if there was some additional information that would be helpful. Wow. This is one impressive piece of engineering. It's patent #4,989,686 dated 5 February 1991 for those who care. There's tons of info in there, also some diagrams which I would really like to see (logic flowcharts, schematics, graphs of various clutch command signals). The patent also confirms the suspicion of a PWM signal from TOD to clutch, as well as a feedback signal from clutch to TOD.
I could not view the drawings however. If anyone can figure out a way to view them (free), please snatch them and post them here -if it's legal.

[VehiGAZ]

One of our patent attys is on the case right now. I'll post the diagrams if he can get at them and its legal.

[VehiGAZ]

Sweet! I got it. And it's all nice-and-legal. Apparently, all anyone needs is to be set up for viewing .tff files to see the diagrams.

I have it in a 1.9 MB .pdf file, but I can't upload it for some reason. Is it too big? Is the site just having some difficulties? Anyone know?

[bobmumgaard]

Thanks for digging up that patent mbeach. It sure has alot of information about the logic and control systems of TOD. The techs at Borg-Warner put together quite a system here. And the price of the TOD ecu now seems somewhat reasonable. The amazing part is that they didn't put in any user control, it certainly would have been pretty simple compared to the amount of work they put into the system. (maybe it was a liability or marketing issue)

After looking through the patent it appears that the signal to the clutch is PWM and if we cut that wire we need a dummy load (to satisfy the feedback requirements of the TOD computer) Other than that there might be still be more than one way to skin this cat.

I think I am going to apply my modifications after the TOD ecu only, as I dont want to fry such an expensive component. After studying the wiring diagrams for awhile I think it might be relatively simple to alter the dash lights along with the TOD ecu-solenoid signal.

Heres my plan:
I want to control the sysem with a knob, probably 5 positions like mbeach stated earlier: Auto, 2wd, ~15%, ~30%, and 50/50

I want to create a pin-to-pin harness between the wiring harness of the vehicle and the TOD ecu (to minimize cutting stock wires), this would make the modification very reversable and easy to install for most anyone. (literally "plug and play")

I plan to cut the ecu-solenoid wire with a relay, so when the knob is in auto mode everything functions normally. Then when the knob is anywhere other than auto mode the ecu is connected to a dummy load and the solenoid receives the signal from a PWM controller.

The PWM controller will probably be a 555, or 556 timer set up to send a 50Hz signal. The controller will be voltage controlled, with the control voltage coming from the 5 position switch. (with the descreet voltages set up by finite resistances)

To accompilsh the correct display lighting I was thinking about interputing the stock wires for the auto, and 3 bar lights with transistors, wired so when the knob is in auto mode the lights are controlled by the TOD ecu normally, but when anywhere other than auto, the lights are disconnected from the ecu. (this darkens the auto light, and allows the 3 bar lights to be controlled by the knob position; see next paragraph)

Then another set of transistors would connect each individual bar light to the illumination wire depending on what position the knob is in. (this lights the 3 bar lights up correctly)

And the whole thing could be bipassed by a relay controlled by the 4low switch, so if you took the transfer case shifter out of Auto the TOD ecu would have all electrical control

I have a rough circuit diagram drawn up right now, and it seems to look like it should work. I plan on spending some time in the University's electrical engineering lab tonight or tommorrow setting up the circuit and performing tests. I also still need to look at a few things in the VX before I go too far.

[mbeach]

...Took the words right out of my mouth.

That's exactly how I plan on doing it. The dash display is not going to be too difficult either. Thanks all for getting the ball rolling on this -it seems like we might have a plan on the way.

Also, I'm sure that you noticed the 4hi switch on the schematic. I mentioned to vehiGAZ (whose TOD ECU I am buying -just in case) that turning this on with the 4lo switch off, should activate a 4hi input to the TOD. There are only 3 states listed in the diagram, with the missing state being a 4hi.

I'm splicing in a few bullet connectors this weekend. They should make diagnostics/testing easier. I'm also charging up the batteries on the Fluke 'scope as we speak.

I would also like to have some OEM type connectors for a true plug and play option -I had hoped that Newark or Tessco would have these as I deal with them often. No such luck however. Do we have an Isuzu hookup that can I.D. and locate the C43 and C44 connectors?

[Tone]

I don't know if this has been mentioned in this thread but realize when you open the circuit to the clutch it is NOT in 100% 2WD mode, there is still plenty of torque going to the front wheels, enough to snap the front drive shaft when on a 2 WD Dyno - been there, done that. That is also a factor why gas mileage does not measurably increase with the current TOD disconnects out there. Good luck and I hope ya'll can make the whole thing work as planned.

[Ldub]

as well as be easily installed and removed by anyone with fingers.

I can tell that if this comes to fruition, It'll be a good mod for me...cuz I have fingers!!! :)
Good work you most admirable brainiacs, Ldub

[mbeach]

...but realize when you open the circuit to the clutch it is NOT in 100% 2WD mode, there is still plenty of torque going to the front wheels.

:eek:
I did not know that.
I was hoping that it would be in 2wd until the VSS tells the TOD that the truck is moving faster than 5 mph.
That means that there must still be a mechanical connection somewhere.

I'll see what the PWM signal is at <5 mph vs. >5mph.

Also, there's a few suspect pins on the connector. There is a 4wd output at pin 3 that I want to look at in addition to the solenoid wire at pin 4.

[mbeach]

Eureka!

Please bear with me.

We are working on motion distribution NOT torque distribution.
We should be concentrating on torque distribution via the electromechanical clutch.

There is no axle disconnect on the VX, and the transfer case has no allowance for any 'freewheeling' of the front axle. The design of the transfer case is such that the front axle (and wheels) are ALWAYS driven at the same speed as the rear driving wheels. Rotational speed is NOT torque. Torque only exists when there is resistance to this rotational movement. This resistance is applied by two things: the electromechanical clutch, and the ball/ramp mechanism (see figure 3 and 4, as well as page 16-17 of the patent). The ball/ramp design of the coupling mechanism is NOT self locking UNLESS there is a control input. Resistance to movement (at the front wheels) provides this control input just as well as activation of the e-clutch.

This explains Tone's snapped driveshaft. The solenoid was deactivated, yet the speed differential between the front and rear axle was great enough to allow the ball/ramp clutch to force the rotor away from the connecting sleeve -this action transferred (almost) 100% of the available torque to the front axle and BOOM. Tone, did your dyno graph suddenly fall off just before your driveshaft went?

The E-clutch provides a means of modulating torque by applying measured resistance to motion according to a predetermined pattern.

Assuming that I haven't completely lost my mind, there is NO WAY that we will ever have true 2wd without an axle disconnect feature.
So, that leaves us with modulation of the e-clutch's holding power via PWM. This can be done only as long as both driveshafts are turning. If the front driveshaft should stop suddenly (like it is dropped into a hole under power), expect the ball/ramp clutch to do its work, regardless of what setting the manual TOD switch is in.

[newthings]

So, if a CV joint is broken and you have unlocking hubs and you lift the blue wire, the front diff will still spin the broken joint/axil?
Roy

[Maugan_VX]

Let me be the first in this thread to say....

.
.
.
.


YAHTZEE!

[mbeach]

Newthings, I am inclined to say "yes." To tell for sure, one of our dyno jockeys could leave the drive shaft in and jack up the front of the VX during their next 2wd pull.

Maugan, if this is something that you knew for certain, please save me the trouble of figuring it out for myself. If it weren't for Tone's post, I would have completely ignored the ball/ramp mechanism, which would have led to big trouble had I decided to test my 'new' 2wd mode by doing donuts in the parking lot.

This doesn't mean that we can't modulate the clutch to go above the 15% that it seems to like (in '2wd') however.

It just means we can't have true 2wd. We might be able to use locking hubs to disconnect the wheels, but that driveshaft, diff and those axles will still turn.
I still want to pull the signals off of some wires to confirm this, but I believe that this (the mechanical connection) is certain and un-bypassable (?) in a non-SOTF transfer case.

There is a TOD Trooper in a friends' junkyard nearby...

[Maugan_VX]

I know not about the drive shaft issue.

All I know is that we're getting close to a dial on my dash for Torque to front!

and that's cause for silly celebration :)

[Child's Play]

Man, this sounds sweet. I'm in the same boat as VehiGaz. If I could just have 4-High constantly at the turn on a knob or push button, that would be enough for me. Anyway, I'm completely lost in the post, but I did see this on E-Bay and thought it may help you guys out. Thought I would try to help out in some way, since I don't have clue one about what you guys are talking about. Here's the link:

http://cgi.ebay.com/ebaymotors/2000-Isuzu-VehiCROSS-Electrical-Troubleshooting-Manual_W0QQitemZ8013213636QQcategoryZ6762QQrdZ1QQc mdZViewItem

[mbeach]

I am marlon506 and I am high bidder.
If I don't win, I hope that SOMEONE here does get it.

So instead of 2hi, 4hi, auto and manual modes, we can do an AUTO, MANUAL, 4HI.
That sounds reasonable, and the manual mode can be controlled via potentiometer (by modifying the control voltage to the timer circuit).
We can use Bob's transistor arrangement to control the dash lights.

The only catch is:
We can only vary the torque to the front axle as long as it is GREATER than what is actually required.
If the speed diferential between front and rear axles is too great, then expect the mechanical 'clutch' to engage the front axle. So no donuts or dynos in 15% mode.
I can live with that.

[bobmumgaard]

http://cgi.ebay.com/ebaymotors/2000...Qc mdZViewItem

Anyone know if this is includded in Tone's Cd? If not, (or even if so) is anybody going to snap this up and maybe scan it for others to use? It would be a great addition to overall knowledge about the VX in addition to the specific issue we are discussing.

If not I'll start bidding, and post it when if I win it.

[bobmumgaard]

mbeach, you beat me to the punch, its all yours

[mbeach]

Bob,
As an ME, do you think that my assessment of our situation (no 2wd) is correct?

Oh, and I've already bid on the book. Believe me, it's knowledge will flow forth like water...

[blacksambo]

If it's any help there is a 1999 version of this booklet offered on a consistent basis on:www.books4cars.com for $40.00. It seems likely that 1999 technology would be the same as 2000 VX's.

[bobmumgaard]

Tone-
Your axle breaking could shed alot of light on this whole subject. I did a search but couldn’t come up with anything. What exactly happened? I assume it was on a dyno pull. So it was probably in third gear and strapped down with no power to the TOD ecu. Where did the axle break? What rpm? (and thus speed of rear wheels, and speed differential between front and rear) What did the break point look like? Was the break plane smooth, jagged, notched in a pattern, did it look like it snapped or did it deform ductilly? I have a few theories about how it could have happened but they depend on the exact situation, and I could be absolutely wrong on them.

[mbeach]

I know where you're going with that thought. I considered it as well. It would be extremely difficult to do a failure analysis at this point, with no photographic or video evidence of the break. I also would like to see the fracture, measure the diameter and wall thickness of the driveshaft, and see if I could come up with a torque value that could have produced the failure.

I can guarantee that it was more than 15% of 230 lb/ft for sure.

[VehiGAZ]

So I've been wondering (as I've been learning)...

The normal operation of the ToD system on a slippery road will transfer torque up front to keep the front wheels spinning about the same as the back wheels, right?

Then it backs off of that torque bias when you come to a stop - partially because you don't need it when stopped, but also (and I am speculating here) to protect itself if you make a sharp turn from that complete stop - in that case, the full 50/50 bias setting may not allow enough rotational speed differential between the sets of wheels and you'd get wheel spin from an axle unwinding, you'd slip the transfer case differential clutch (if you were on dry, grippy pavement that didn't allow for any wheel spin). It makes sense that you wouldn't want any torque transfer to the front while turning at very low speeds (i.e., when starting from a stop).

Well, if we come up with a switch & circuit that will tell the transfer case differential clutch to keep applying a full 50/50 torque split all the time, won't we be asking for trouble in those types of situations? On a snowy road, an axle can unwind pretty easily by letting a tire slip, but if you were turning onto a clear road, wouldn't that stress on the transfer case differential still be there? And wouldn't that be not-so-good?

I freely admit to speaking in total ignorance on this subject (as I said, I've just started learning about how differentials and transfer cases work) - I'm just trying to follow along with the other discussions.

I have come to one conclusion, though - the Trooper ToD conversion in the first post is not as easy to implement for the VX.

Any thoughts?

[mbeach]

The Trooper TOD conversion (as documented and implemented by Tad (Nazrat)) is a fine piece of work in its own right, however, a few of us have not used it because it has a critical flaw.
The e-clutch uses a very low resistance coil, 1-5 ohms maximum. This coil was designed for a PWM input from the TOD computer. By locking it up with straight DC voltage, you risk burning out the coil because it no longer has the ability to modulate its holding power (at the millisecond rate, which is not detectable). You are simply forcing it to stay locked. I had to look this up in order to better explain it. Here's a quote that I found that seems to put it in better terms:
"...This is why PWM drive is the best for solenoids. A solenoid designed for PWM drive will have quite a low coil resistance. If DC was applied to it, the coil would heat up and burn out. It is the inductance of the coil on a PWM signal that restricts the current to safe values. Of course this means that if for any reason the plunger gets stuck in the "out" position, where the inductance is low, the coil may burn-out..."

Now, this has not happened yet, but I fear that prolonged use in 4hi could cause this to occur when using the 'power mod'.

What I am proposing, and I suspect Bob is doing as well, is to modify Tad's work by replacing his 12V signal with a PWM signal. We are NOT reinventing the wheel here, we are simply making it safer and more flexible.

By using the PWM generator, we can vary this pulse/duty cycle to provide a variable torque split as opposed to the all-or-nothing 4hi. We can also tie this controller into the dash display with Bob's transistor arrangement.

As for your 4hi question, Yes, you are correct. 4hi should not be used on dry pavement. You should leave the TOD in the AUTO mode for such applications.

I have started streamlining the circuit, and should have a paper copy done by Monday. I have drifted towards a single (dash mounted?) pushbutton switch, labeled MANUAL that will turn off the TOD Auto mode. When MANUAL is engaged, the PW can be varied from 0-88% by means of a knob, mounted next to the winter/power buttons. All with appropriate dash displays.

Just keep in mind, we cannot request LESS torque than what is required for the driving situation.

[VehiGAZ]

Okay, so I'm learning something.

So the 555 you speak of is some sort of signal generator capable of creating a PWM signal? Can it modulate it too?

[bobmumgaard]

I've spent a few hours studying the patent and look at the maintenance manual and I think I have a pretty good idea about how this thing is assembled and how it operates. Though I would love to get one on the bench to take apart and examine.

About torque:
mbeach is correct that you can only transmit as much torque as something (say a wheel) can hold. This means that if the wheel was on ice, you could send torque to the wheel until traction faltered and then the wheel would just spin, So if you are sending torque to the rears and they are spinning, trying to send more torque causes the wheel to spin faster, nothing more. Now if the wheel is locked, say the VX is strapped down on a dyno and you send alittle torque to the front, nothing will probably happen. If you send more and more torque eventually the wheel will either start slipping against the ground, the straps will snap or you will break something in the drivetrain, say an axle.

Construction of the transfer case:
It seems to me that the clutch works very much like a Cusco or Kaaz limited slip differential. This means that they do allow a difference in rotational speed front to rear. And this makes sense because otherwise it would be the equivalent to a true mechanical lock. If the front and rear HAD to spin at the same speed it would be like driving in 4Low all the time, lots of scrub.

The transfer case appears to take the output from the engine and transmits it to the rear wheels through a shaft, much like there is just a driveshaft and no transfer case. This means the rear is powered all the time, no matter what and always spins at the same rate as the transmission output. (unless we activate the planetary gearset for 4low) On this shaft is a sprocket, this sprocket is connected by a chain to another sprocket on the front driveshaft. Inside the first sprocket (the one on the mainshaft) is the clutch. The clutch appears to consist of 13 friction disks. 6 of these are attached to the mainshaft, (and thus spin at the speed of the rear wheels) and 7 are attached to the sprocket (and thus spin at the speed of the front wheels) These disks alternate, one for the rear next to one for the front next to one for the rear and so on..

There is then an inductive coil that creates a magnetic field when we send current through it. This coil squeezes all the friction disks together. So when we power this coil up the squeezing action increases the friction between the front and rear shafts, this means we take some of the torque we were sending to the rear and send it to the front. Now the front might not move, if the wheels were in a tough spot then the clutch would just slip. Squeeze harder and you get more friction=more torque. Keep squeezing and eventually the front wheels will either move, something will break or you will be squeezing your hardest and the friction disks in the clutch will still just slip. However, in normal situations, if you squeeze the front will start to spin at same rate as the rear, and if it doesn’t, the TOD ecu just squeezes harder until they spin at the same speed (or the ecu is happy with the speed difference)

The system is the same in a clutch type limited slip differential like Cusco or Kaaz, we just modulate the squeezing electronically; they do it with elaborate shims. And the same principle as the multidisk clutches you see on high torque cars.

In fact, this is almost the same system we see on any car’s clutch. In that case, your foot controls the squeezing, and the clutch slips, it is still transmitting some torque even though it’s slipping. Hopefully the clutch eventually stops slipping and is then transmitting 100% of the engine’s torque to the wheels.

The ball ramp system appears to be there to make sure that the clutch doesn’t self activate. (Imagine if it did at 75 mph, dangerous liability there) and it doesn’t appear to be able to transmit very much torque, atleast not enough to break a driveshaft. Though I am still looking the whole ramp thing over, but this is my initial assessment, though I could be wrong. In addition to its small size, I don’t think that the ball ramp system is involved with any automatic torque transfer because if it was the clutch would be a VERY expensive redundancy.

So… the moment we are waiting for….can we get true 100% 2wd? In my opinion not 100%, but maybe 95%

Because the friction disks are always in some contact, and there are so many of them they will always create some friction, even when there is no squeezing from the solenoid. How much friction (and thus torque) probably depends on how fast everything is spinning.
This means that if you take off the front driveshaft, the front output of the transfer case will still turn. Also, if you break a CV joint and have the TOD disconnected everything will still spin due to this residual friction. An interesting experiment would be to disconnect the front driveshaft and connected the transfer case output to a brake (like an engine brake used my manufacturers to dyno engines) and measure this torque.

A more practical experiment would be to put the TOD control we are talking about in a VX (I think we are on the right track with electronic systems discussed above). And take the VX to a brake based dyno. In fact, dynopack is the most common brake based system. This dyno attaches a large brake to each hub of a 4wd car and applies a variable resistance to the wheel. This resistance measures the torque each wheel is putting out. (most dynos are inertia based (use rollers) and measure power and then infer torque, the opposite strategy as a load (brake) based system)

If someone really wants to find out the exact characteristics of the TOD system, find a dynopack system. They are used for rally cars most often, so the best bet is to find a place that works on STi’s and Evos. Unfortunately for me I’ve never located a dynopack system within a few states of Nebraska.

Load based dyno info:
http://www.mustangworld.com/ourpics/News/nowheel.htm
http://www.dynopack.co.nz/

Limited slip info:
http://auto.howstuffworks.com/differential8.htm

Normal car clutch info:
http://auto.howstuffworks.com/clutch.htm

About the mechanical lock
When we put the transfer case in 4Low it slides a mechanical lock between the front and rear axles. (actually the mainshaft and sprocket) In this situation the clutch is completely out of the loop. This means both axles rotate at the same speed no matter what. So if both front wheels where on the ground and the rears where not (imagine the VX hanging off a cliff, scary aint it?) then the car should be able to pull itself up (assuming enough traction and engine power) in this situation the fronts receive 100% of engine torque because of the mechanical lock (there can’t be any slipping) and because the rears cannot transmit any torque because they would be spinning against air at the same rate as the fronts pull against the ground.

Well alright, sorry this was so long, just trying to hash out the exact nature of the things we are working with here.

And again, I could be completely wrong on all this. What are your guy’s thoughts?

[mbeach]

We can vary the duty cycle of the square wave produced by the timer circuit by changing the control voltage that is applied to the 555.

In theory, we can have an infinite amount of variation to the solenoid control signal this way. In reality, I would like a (now) 3 position (knob) switch, that will correspond to the dash indicators as well as the 15/30/50% torque values that we want to select.
Push the MANUAL button (maybe use the spare foglight switch that I have laying around), and turn the knob all the way to the right for 50% (or 4hi).

If I should forget and leave it in MANUAL mode (signified by the light on the switch, and the lack of an AUTO displayed on the TOD display), it should be alright as long as the speed differential (aforementioned donuts and dynos) is not so great as to activate the ball/ramp mechanism. After all, the truck is in 15% mode 99% of the time anyways.

EDIT: My first sentence was in response to VehiGAZ' question.

Bob,
I'm still fairly certain about the ball/ramp's ability to transmit large amounts of torque to the front driveshaft. I thought the same thing about the redundancy of the e-clutch, but I believe that its primary purpose is to proportion/modulate the amount of torque to the front, rather than to simply link the two shafts together.
I don't believe that mere residual friction among the clutch packs could be responsible for the broken driveshaft. A clutch pack would've slipped long before steel failed.
Also, why would the Trooper's designers implement a Shift-on-the-fly mechanism if they could simply release the e-clutch and achieve the same result?

[bobmumgaard]

I agree with VehiGAZ and mbeach that 4hi would be bad in dry situations, and the TOD handles theses with ease. It is the times when TOD is overactive, trying too hard on snow and ice that we are looking to correct. Not to mention the need of the mechanically inclined to have COMPLETE control over the machines they use.

So the 555 you speak of is some sort of signal generator capable of creating a PWM signal? Can it modulate it too?
The 555 is a timer chip. You can use it along with capacitance, resistance and a transistor to create a PWM signal. This signal is varied by varying a control voltage into the 555 chip. So yes it is exatly what you speak of.

I agree with mbeach's assesment of the trooper mod. The coil is not meant for the prolonged current a constant 12V source provides. And a PWM signal would be more inline with an OEM solution.

I was working toward a knob with 5 poles (and thus 5 positions): Auto, 0% torque, 15% torque, 30% torque and 50% torque. This makes wiring the lights up easier (since youre working with poles instead of an infinte knob). And it can be wired to elimate the manual button.

I really need to clean up my circuit diagram so I can post it.

[mbeach]

Poop.
Posts are out of sequence.

[mbeach]

Here's what I can do:
-A MANUAL/AUTO switch. Tie it in to the same place as the Trooper Power Mod has it located.
-Replace the relay in the power mod with an appropriate timer circuit/PWM generator.
-Implement a knob, that by varying the values (vdc) applied to the timer circuit, will vary the PW of the output signal to the e-clutch.

Things that I need.
-Values, voltage and duty cycle, from the TOD to the e-clutch. This weekend I am splicing in taps to some (o.k., a bunch of) wires. I will be driving around with a Fluke 97 on my passenger seat for a few hours.
-I also want to gather all of this data for each condition (15/30/50/4lo/N) from every conceivable input source (TPS, ABS, Front and rear VSS, etc.). I also want to peek at the 4hi and 4lo switches that I see on the schematic.
-A plan to control the dash lights. Transistors is the way to go for sure. I need to think this through later though. Must collect data first.

I'm not going to promise anything, but I should have a handle on those duty cycle readings by monday.

[VehiGAZ]

I think you two are on the right track here! Thanks for the layman's explanation of how the transfer case works, and what happens when you shift into 4WD-low, Bob. VERY helpful to me!

So I think we should be fine if we come up with the circuit that allows us to generate the right signal to the ToD transfer clutch. It is used to having some current on it all the time - but it's best to mimmick the "natural" signal it gets - VDC is probably a bad idea in the long run.

I think my concerns about having the full-4WD-Hi activated constantly are not a big deal as long as we pay attention to what we are doing. Whatever stresses we put into the drivetrain will undoubtedly release themselves in that clutch pack.

Alrighty then - you EE types figure out that circuit. It would be nice if we could find extra ToD ECU wiring harness connectors - that way, it could be set up to plug right in in-line.

Thanks again!

[mbeach]

Alrighty then - you EE types figure out that circuit.
I'm an MEtech working in an EE's position. I think Bob's an ME as well. That's why we're overanalyzing everything ;)


It would be nice if we could find extra ToD ECU wiring harness connectors - that way, it could be set up to plug right in in-line.
I want these plugs soo badly. As it stands, this will not be a fix for the faint of heart. With the plugs, we could build them and just send them out to be plugged in.

I am at 'work' right now. Getting ready to build the interface cables that I need to test the TOD's ins and outs.
I'll take pictures.

[bobmumgaard]

I'm still fairly certain about the ball/ramp's ability to transmit large amounts of torque to the front driveshaft. I thought the same thing about the redundancy of the e-clutch, but I believe that its primary purpose is to proportion/modulate the amount of torque to the front, rather than to simply link the two shafts together. mbeach

After further review, there is no indisputable conclusive evidence that my analysis of the ball ramp thing is right and the play stands as called on the field by mbeach

Afterall, the techs at Isuzu went through alot of trouble to put the ball-ramp mechanism in there. And SOMETHING had to cause Tone's broken axle. And I certainly don't think it was residual friction from a few ~5 inch disks.

I think someone should call Merlin and see about finding the supplier for those connectors, they would make this a fool-proof modification. Right now I am looking at tapping or modifying 9 different wires (though i am trying to reduce this #). I talked to a contact at Bosch but they weren't very helpful.

mbeach, I drew up my circuit diagram on SmartDraw and am looking it over. I think the next step is to find those PWM values for the solenoid, and Voltage values for the other important wires And while youre in there, some data on the real currents the solenoid is drawing might be helpful to us when it comes time to select timer components. If I had a portable scope I'd be in the VX confirming your numbers but right now I am using aTektronix TDS 210 that is chained to the lab.

VehiGAZ, glad to help, and I hope I got everything right on my analysis.


I'm an MEtech working in an EE's position. I think Bob's an ME as well. That's why we're overanalyzing everything

If only ME's built everything: We'd run out of titanium, parts would start at 1million dollars, everything would fix itself and the world would be bombproof.
Mechanical Engineering: the definition of 8 gallons in a 5 gallon bucket.

[Tone]

Front driveshaft snapped at about 90MPH on the dyno during my second pass. It broke about 2 inches out the the transfer case (required replacing it also) and was a bit jagged. Made a loud pop when it happened.

[mbeach]

I'm working on uploading photos and data (spreadsheets) now. All that I can say is AWESOME.
Everything worked like a charm (a tribute to my cable-building and soldering skills ;) ).

There were some VERY interesting occurences during testing.

Things of note (to get us started before the pictures are up):
-The frequency of the PWM signal to the e-clutch is 50 Hz. Duh, 20 milliseconds. I remember reading that in the literature for the VX.
-In "2wd" mode, below 15% torque to front, the TOD is sending current to the e-clutch. The PWM signal = 3.2V. This is a 22% duty cycle based on my input voltage.
-My voltage into the TOD was 14.0V even. This will skew results a bit, but it still works. Plus the math is easier.
-The pulse width varies with speed, more speed = greater duty cycle, even if it's still in 15% mode. At 30mph, the PWM signal = 5.5V. This is a 39% duty cycle.
-Anything above a 68% duty cycle will put the truck into 4hi (spinning tires, low speed). This signal should be increased proportionately with respect to vehicle speed. At 68%, we are seeing only 9.5V at the e-clutch.
-Contrary to my reading in the patent description, ABS does NOT turn off the 4wd.

I have plenty of photos, plus some screenshots of the scope and TOD in action. I'm trying to put in into my gallery along with an excel file with my data collection.

[mbeach]

O.K., this is a bit unrehearsed.

This was the cable that I built to interface to the TOD:

http://www.vehicross.info/gallery/data/500/thumbs/P2130001.JPG (http://www.vehicross.info/gallery/data/500/P2130001.JPG)

This was the cable map, it shows what parameters were monitored:
http://www.vehicross.info/gallery/data/500/thumbs/cablemap.JPG (http://www.vehicross.info/gallery/data/500/cablemap.JPG)

Here is the TOD connector:

http://www.vehicross.info/gallery/data/500/thumbs/TODview.JPG (http://www.vehicross.info/gallery/data/500/TODview.JPG)
I spliced into this with my cable. Connections were made inside of the plugs (which are impossible to dismantle by the way. If anyone knows how to take these things apart, please let me know. I was forced to solder INSIDE of the holes underneath the white clips.)

TOD interface cable, ready to go.http://www.vehicross.info/gallery/data/500/thumbs/Interface.JPG (http://www.vehicross.info/gallery/data/500/Interface.JPG)

Here's the road we used for testing. Old Murphy Dome Rd., about 18 miles north of Fairbanks, Alaska. This road starts out as packed gravel, frozen with patches of hard snow and ice. It quickly peters out into a narrow trail, all ruts and deep snow, about 5 feet wide. Yes, I scratched the truck -a lot.
http://www.vehicross.info/gallery/data/500/thumbs/OMDroad.JPG (http://www.vehicross.info/gallery/data/500/OMDroad.JPG)http://www.vehicross.info/gallery/data/500/thumbs/GoatPath.JPG (http://www.vehicross.info/gallery/data/500/GoatPath.JPG)

This is my lovely co-driver, whose patience was sorely tested this day. "...I said SPIN the tires woman!"
http://www.vehicross.info/gallery/data/500/thumbs/Co-driver.JPG (http://www.vehicross.info/gallery/data/500/Co-driver.JPG)



This is a scope shot taken at idle, in Neutral (transmission). Notice the pulse width. http://www.vehicross.info/gallery/data/500/thumbs/GoodIdle.JPG (http://www.vehicross.info/gallery/data/500/GoodIdle.JPG)

At 60mph (on ice) in 15% mode:http://www.vehicross.info/gallery/data/500/thumbs/60mph.JPG (http://www.vehicross.info/gallery/data/500/60mph.JPG)

Random scope shot:http://www.vehicross.info/gallery/data/500/thumbs/15drive.JPG (http://www.vehicross.info/gallery/data/500/15drive.JPG)

I need to attach an .xls file. how do I do this?

[mbeach]

I have it on pdf now and still can't attach it to the post. What gives?

Here's a caption for the file if I can ever upload it.
"If there's a blank, it was not important enough to fill in. I chose not to mess with the ABS leads after I determined that it had no effect on the TOD. I'm sure that the TOD uses the ABS as an input, but the 4WD Out to the ABS is unreadable.
TPS signal is variable via potentiometer at the throttle. Roughly 0-13V.
The VSSs are weird Hall-effect sensors operating at 4-5V.
The indicators work as explained in the maintenance CD. Switched grounds indicate an "on" state."

[VehiGAZ]

You soldering fool! WOW mbeach - you have gone above and beyond the call here! I am truly impressed by what you have done to get this nut cracked.

As for the Excel file, there is a size limit on attachable files, which I ran into when trying to post the ToD patent file. Moncha PM'd me about it, but of course I deleted the PM so I can't tell you what the limit is. But if you have just a data spreadsheet, it shouldn't be running into the size limit. Alternatively, you can try to post it in the Downloads section of the site, but I didn't have much luck with that, either. It seemed to want a URL for the file - I wasn't sure.

So although I absolutely LOATHE drawing conclusions or even being guided in my research by initial data, don't your findings suggest that we shouldn't send a static 68%+ signal to the clutch? That is, wouldn't it potentially be too much when you are accelerating from a stop? Or no?

The difficulties with the wiring harness shouldn't be a big deal. If we just need to tap into one wire (the one going to the ToD clutch), it's just not worth rigging up a dedicated connector. Of course, judging by what you've done already in the cable-making department, I realize you may not agree with me :-). It can still be a simple install to cut the clutch wire and splice in the switchable circuit.

Ok, good luck with the data interpretation! Let us know what else you figure out!

[mbeach]

Having the correct plug (we only need one of the two) would make life much easier, and it would look nicer.

As far as I can tell, we only need to cut/intercept 1 wire. The pink TOD to solenoid wire. We will want to 'tap in to' 4 more wires, each for the 3 display segments and one for the AUTO display.

That's 4 taps and one cut. Not too bad, even for a novice. We just have to make sure that everyone uses high-quality taps (if there really is such a thing). Vibration is the enemy of the wire tap (scotch-loc, et al.).

As for the 68% duty cycle for 4wd.
This is a bare minimum number, and at high speed may not be high enough.
The purpose here is not to replace the TOD's logic, we are just trying to modify its outputs. There really is no such thing as overkill as long as we provide a nice 50Hz pulsed signal to the e-clutch.
I say 87-88% duty cycle would work for just about everyone, regardless of battery juice available.

The biggest surprise for me was the presence of voltage at the pink wire when in '2wd'.

[VehiGAZ]

I think you're right - a decent margin above 68% will probably do the trick nicely - and if it's not enough to maintain full 4WD-Hi at 60 mph, well, you probably don't really need 4WD in that case anyway.

So, uh, are you going to throw a circuit together, mbeach? And post required parts and directions? Pretty please? Winter's coming here in Connecticut... :-)

[mbeach]

I'll try to work on this today. I have a lot of parts available to me that may not be readily accessable for most people.
Today I found a really nice trimmer that would make a cool knob. Very tactile with nice feedback. It felt like a BMW iDrive unit. It could be easily replaced with a 2k ohm potentiometer from Radio Shack though.
I'm trying to make it as simple as possible for everyone to build/commission to build.

Reality is, all we did here was to confirm the work that the Terracan guys did. I never was able to look at the links, but from Bob's first post, it sounds like we have just done our own version of the same thing.
I can't take any credit for this, but I assure you that a VX ready solution will be on the way asap.
I'd still like to share my spreadsheet, but I think that we can get started without it.

[mbeach]

It appears that there is a mass-produced PWM controller that will suit our needs. All we need now is a pot, a knob, and the ability to ground the indicator lights at will. This can be done through the same pot(entiometer) that selects the 4wd mode.

It's getting easier and cheaper by the day.

[Maugan_VX]

mbeach, if this works, and its simple enough for me to pull off in an afternoon's worth of work....


I'll fly out to Alaska and kiss you.

[mbeach]

Ha, I'll pass on the man-love -but thanks anyways.

Actually, when I stated looking back through old posts, it hit me that we (the board) were on to a solution a long time ago.
Especially in this post by SGT. Batguano:
"It may be a Pulse Width Modulated signal, like the speed signal, which is why no one has come up with a soultion to the top speed limiter of our ecu.

I may be wrong, but I've been under the impression that you can use a dc motor controller on a pwm circuit. So, I'm wondering if one could replace the rheostat or variable resistor on the dc controller board with a 4-position switch and four fixed value resistors."

And that's exactly what I've come around to. I found a DC motor/fan/lamp PWM controller that will work nicely, and only cost between $40 and $50.
That unit, a switch to activate MANUAL mode, and a rotary switch (no longer a potentiometer -long story) to select the modes and we are looking at a $75 mod, depending on how fancy you want to make it look.

I'm ordering a PWM controller from Critical Velocity today for testing.

[Thelgord]

I realize this is an old and probably dead thread, but did this ever work?

[ipd]

I'd also like to know. Although I realize that the odds are that even if someone who pulled it off still has his/her vx, they aren't apt to post on this forum anymore.

[Thelgord]

Yeah, but maybe someone knows someone who knows someone else? LOL!

[blacksambo]

Yeah, but maybe someone knows someone who knows someone else? LOL!

There is a physical ball ramp mechanism in the way of ever governing the TOD with merely electrical switching. Everybody who has tried didn't succeed. You can get a Trooper unit and install it easier. The VX was a deluxe Trooper , and a key selling point was it would always be instantly ready for whatever the terrain and weather threw at it.
If you have to turn it off and on manually it wouldn't be always ready to react.
Sorry.