Torque on Demand

[Hummer Aficionado_VT]

Can someone explain to me a little more how TOD works? Is it AWD?

[ojmagg]

Torque-on-Demand is a hybrid between part-time four-wheel drive and all-wheel drive. Isuzu, in conjunction with Borg-Warner Automotive, created the patented Torque-on-Demand system. This system performs like a conventional part-time four-wheel drive system when the transfer case is in the 2 High (two-wheel drive/High-range) position or the 4 Low setting (four-wheel drive/Low-range). When the transfer case is set to the "TOD" position (which stands for Torque-on-Demand), it acts like an all-wheel drive system.

The following components are contained in the Torque-on-Demand system: An electromagnetic multi-plate clutch (which is located in the transfer case), a computerized control unit, front and rear speed sensors, and a throttle position sensor that monitors engine output.

In the TOD setting, the amount of torque transferred to the front wheels is determined by the amount of force pressing on the clutch - when the clutch is completely disengaged, only the rear wheels are driven; when the clutch is completely engaged, a 50/50 torque split is achieved (50 percent of the torque goes to the front wheels and 50 percent of the torque goes to the rear wheels). The torque split (the amount of torque transferred to each axle) varies continuously as the vehicle is driven.

Briefly, here's how it functions when driving: When the transfer case is in the "TOD" position, the Torque-on-Demand control unit receives signals sent from the speed sensors and the throttle position sensor. Based on that input, it varies the amount of force that's applied to the clutch. When the rear wheels begin to slip, the control unit detects the slipping and determines the optimum level of torque based on the feedback control logic, and then increases the torque to the front wheels.

The control unit also uses the signal from the throttle position sensor to predict future conditions - including acceleration and deceleration - then determines the torque distribution.

Isuzu vehicles equipped with TOD have a TOD indicator lamp on the instrument panel that provides the driver with active feedback regarding the performance of the system and the torque split status. There are four lights on the TOD indicator, representing:

One bar illuminated: approximately 100 percent rear-wheel drive; 0 percent front-wheel drive.
Two bars illuminated: approximately 85 percent rear-wheel drive; 15 percent front-wheel drive.
Three bars illuminated: approximately 70 percent rear-wheel drive; 30 percent front-wheel drive.
Four bars illuminated: approximately 50 percent rear-wheel drive; 50 percent front-wheel drive.
Torque-on-Demand can make changes as quickly as 20 milliseconds (or, in the time it takes for a fly to flap its wings once).

Torque-on-Demand is superior to passive all-wheel drive systems (like those using a viscous clutch) because it responds to specific driving conditions. For example, some competitive systems don't know the difference between turning a corner, or slipping the tires in mud. That type of system often overreacts, providing more torque than is needed, and it is not as quick responding to the changing conditions.

The primary benefit of the Torque-on-Demand system is that the driver can select the TOD setting and leave it there for all driving conditions. The vehicle then makes all the decisions and provides positive feedback (via the TOD display on the instrument panel) so the driver is aware of how the system is functioning. Then, if the driver ever needs additional traction, he or she can select the 4 Low setting.

Thanks to the variable torque split, Isuzu vehicles with TOD have superior handling in adverse conditions because it constantly adjusts to the available traction. In addition, the Torque-on-Demand system anticipates what will happen next and adjusts the torque split accordingly. For example, if a driver is going down a hill and takes his or her foot off the accelerator, the TOD system automatically increases torque to the front wheels to improve handling and stability. Best of all, this happens without the driver sensing any changes. This makes the Isuzu vehicle more sure-footed and better balanced.

It took 12 years to develop this Torque-on-Demand system. It was first introduced in off-road racing trucks, where it had to handle engines producing between 800 - 1,000 ft.-lbs. of torque.

[etlsport]

nice description.. a few things are different/ misleading about the VX though

on the VX you can't select TOD or not, with the VX you are either in 4Hi (TOD, normal driving) or 4Lo..

the part about the bars is misleading too.. there is a digram of the vehicle with each of the rear wheels represented by a large light, which is always lit, each of the front wheels is represented by three lights, when none of them are lit 100% of power is in the rear.. almost never happens save for 0-5mph on dry roads.. after about 5mph one of the lights representing the front wheel will light up.. indicating 15% front and 85% rear.. as the wheels slip power is sent to the front and more lights will light up and go out as the TOD system adjusts

[Dino]

I love TOD!!

I live down a 1.5 mile road that starts out patched, broken & nasty asphalt, then turns to bumpy dirt. There are a couple hairpin corners where the TOD really keeps the VX pullin on the line the front wheels are pointing. One such corner is radicaly uphill and sharp left. It's fun to manualy shift to 2nd then feed the throttle on as it just rails it's way around the turn!! The lower the gear you're in, the more sensitive the TOD engagement is to the throttle movement.

I've driven other vehicles on the same turn and had the rear wheels spin. It's a ranch road and I see pickup trucks spinning there all the time.
No spinning with the VX and TOD thank you!!

[Hummer Aficionado_VT]

WOW! Thanks for the amazing description guys. That is very helpful!

[blacksambo]

Now! How does TOD compare to other up to date systems like the new Land Rover Terrain sensing system, and does anybody else offer this type of TOD technology in conjunction with a locked differntial low mode? Thx.

[Dino]

Food for thought ...

I wish I could mate up the hydraulic controled TOD transfer case to a 5 speed manual trans, with an engine driven hydraulic pump so it could all work. Imagine having the TOD capabilities in a manual with better mileage and safer off roading due to the mechanical link betwen engine and wheels.

I'm still seriously considering the manual conversion even though I love the TOD.

[tysamigo]

WOW, thank you very much for the description. I'm not very "mechanical" with cars....yet. I'm learning. This all makes sense, however you would think that someone would have duplicated the technology by now. It's been some time and I haven't seen any other vehicles with it. It all sounds good and I'm VERY glad I have it. It just makes my rig that much more different than the normal vehicle

Is the TOD durable? Are they likely to have problems and are they expensive to fix? Just a few q's for the newbie...

Thanks

[circmand]

I know the idea to match TOD to a manual transmission may seem like a good idea but todays modern automatic transmissions perform better than the driver and get better MPG than the manual transmissions.

[Chopper]

There are 4x Troopers and Rodeos made with the 6cyl/5sp.manual combo...I just don't know if it's the Borg Warner setup, or more of a GM deal. I've worked on both, but never really paid any attention to the transmissions.

[Chopper]

I can think of a lot of descriptors for this slush-box, but modern and efficient would not be among them. This thing has been around since the K car It was not GMs' finest moment.

[blacksambo]

I can think of a lot of descriptors for this slush-box, but modern and efficient would not be among them. This thing has been around since the K car It was not GMs' finest moment.

Is there a better system currently on the market that does everything the VX can do but is "modern and efficient" or was TOD the last word in automatic transfer of power? Just curious as to what is out there.

[Dino]

With cars, Porsche did some very cool stuff with the Carerra 4. Big bucks on the maintenance though...

I don't know of another SUV that has a TOD system.

[Chopper]

I've never had issues with the TOD. It's pretty slick in that you are all but RWD till you need more, then it's there, pretty quickly, and fairly smoothly. I like it at least as much as the Audi/VW system...maybe more...but it's light years behind Acuras' new system. I am talking only about road manners here, because I know absolutely nothing about offroading. My comments were directed at the transmission itself. I generally don't like automatics, and do not care for this one at all. Lexus and MB make some amazing gear boxes, but I'm with Dino, I'd rather do it myself. A manual conversion is tempting. Has been for six years now.

[blacksambo]

I've never had issues with the TOD. It's pretty slick in that you are all but RWD till you need more, then it's there, pretty quickly, and fairly smoothly. I like it at least as much as the Audi/VW system...maybe more...but it's light years behind Acuras' new system. I am talking only about road manners here, because I know absolutely nothing about offroading. My comments were directed at the transmission itself. I generally don't like automatics, and do not care for this one at all. Lexus and MB make some amazing gear boxes, but I'm with Dino, I'd rather do it myself. A manual conversion is tempting. Has been for six years now.

Thanks for the transmision clarification. I'm not so certain about that Acura SH-AWD system. First, it sticks you 90% into front wheel drive until something tricky pops up? Second, that yaw control stuff sounds a little overblown. Meaning they state versus conventional 4WD its better because it automatically splits power between left and right tires. Doesn't limited slip differential do this? So, the only time the Acura's system is of benefit is versus locked-differential mode 4WD's. Is that really all that advanced versus VX's TOD which is biased 90% rear wheel drive with full-time LSD? I'm not so sure TOD has been really eclipsed yet, especially since it's been fairly bullet proof dependibilitywise for 11 years running. Not trying to pat Isuzu on the back here, just trying to guage the true lay of the land today.