Help – I’m using my Tachometer to estimate speed

[E-ZooZoo One]

My speedometer and odometer aren’t working right now…
I believe the problem is the little plastic gear inside of the T-case, since replacing both the speed sensor and the gauge cluster haven’t done the trick.

Until I get it repaired, I’m relying on the accuracy of my ‘seat-of-the-pants meter’ – using the Tachometer to make an educated guess.


I would be extremely grateful if someone with stock (or near-stock) sized tires could give me the Tachometer readings for the following maintained speeds:

25-mph
30-mph
35-mph
45-mph
55-mph


Right now I’m using 2250-rpm in overdrive/4th as my best guess for 55-mph…
I know that’s pretty close, especially since the County Sheriff that paced me yesterday (for about 5-miles!) didn’t pull me over - but I sure wouldn’t mind some confirmation. ;)


TIA!

[MZ-N10]

all i know is a hair under 3000rpm is 80 mph....

[Francesco Rizzo]

hey, I think there's a fuse for the speed/odometer in the fuse box... see if that's blown first.. might help

[crager34]

Is the trip meter still working?

[goffaramma]

Driving into work this morning I checked, and at 2500 rpms I was steady at 65 mph. Other than that, with inclines and gears changing and everything, I had a tough time getting a good indication of what other rpm/mph would be.

[VehiX]

You could always buy or use the Scan Gauge until you get things staightened out. It will tell you the exact speed you're going and even allows for adjustment if you have over sized tires installed :)

http://scangauge.com/

http://www.vehicross.info/gallery/data/500/thumbs/pics2_0101.jpg (http://www.vehicross.info/gallery/data/500/pics2_0101.jpg)

[E-ZooZoo One]

Thanks for all of the replies – Here goes:



hey, I think there's a fuse for the speed/odometer in the fuse box... see if that's blown first.. might help
I looked in both the dash & under-hood fuse boxes…
In the dash fuse box, there was a fuse called ‘meter’ - could that be it?

(I couldn’t check to see if it was blown since the previous owner lost the fuse puller, and I couldn’t get a good enough grip on it with my fingers -- I’ll take a look this evening using the puller out of my Rodeo.)





all i know is a hair under 3000rpm is 80 mph....

Driving into work this morning I checked, and at 2500 rpms I was steady at 65 mph. Other than that, with inclines and gears changing and everything, I had a tough time getting a good indication of what other rpm/mph would be.
OK… in top gear (rounding off)…
If 3000 rpm = 80 mph
and 2500 rpm = 65 mph
then 2000 rpm = 50 mph… or there abouts.

It's no wonder that County Sheriff took such an interest in me. --- With my 255/70/16s taken into account, and using 2250 rpm as my guide, I was most likely maintaining roughly 58.5 mph… which was probably just peppy enough to keep him drooling at the prospect of snagging me for going above 60 mph on a downhill slope.





Is the trip meter still working?
No, it’s dead too.





You could always buy or use the Scan Gauge until you get things staightened out. It will tell you the exact speed you're going and even allows for adjustment if you have over sized tires installed :)

http://scangauge.com/
That looks like a handy little device, to be sure - but if I am correct in assuming that my problem is the little gear inside of the T-case that drives the Speed Sensor, resulting in no signal to the gauges – it seems to me that there would be no signal at the OBD II port either... right?

If that’s the case, then about the only benefit to having that device would be that I could reset the Check Engine Light (which is constantly throwing the code for a Faulty Speed Sensor).



Thanks again everyone...
It looks like I should probably drop it down closer to 2175 rpm for 55 mph until I get this thing fixed. ;)

[Bulldoggie]

Another back-up to the speedometer is the GPS antenna on the laptop. gives exact speed minus one second delay, plus elevation in feet. I have not corrected my speedo for larger tires, so it is nice to see exactly what the error is. In my case it's about 5 mph.

[Francesco Rizzo]

yeah dude, that should be it. All new cars have a fuse for the odometer. I know this because this buddy used to ride around with it pulled so it never racked the milage. Walmart should be a winner, maybe spend 5 bucks for a mini fuse kit for your VX just to start with since you already need that lil prong. I t doesn't hurt to have one. goodluck

[E-ZooZoo One]

Well, I guess it’s a good thing that I didn’t get my hopes up. --- This morning I installed a fresh fuse from my Rodeo’s selection of spares… No dice.

When I have more time (hopefully this evening) I’ll go back and double-check every single blamed one of them, just to be sure – but at this point I’m not holding my breath.


This fix sounded almost too good to be true – but then again, I sort of knew better… I’m never that lucky.


Thanks again just the same.

[Tone]

There is no fuse for the speedo otherwise people would disconnect it to keep the mileage down. The sensor on back of the tranny is responsible for feeding the speedo/odo - if any of the 3 wires there get cut you will have no signal.

[E-ZooZoo One]

The sensor is brand new - and the wires appear to be fine as well…
The gauge cluster was replaced too (and I still have the original).

^ Both attempted repairs occurred prior to purchase, at a local shop, where I know the staff and have talked at length with them about the problem. --- Despite my reservations about buying it with a dead speedo/odo, I have to admit that it was nice haggling point with the seller.


By process of elimination, I’m still thinking that it’s the little plastic gear inside of the T-case – the one that mates to the sending unit… but you can bet your next paycheck that I will be thoroughly checking every single possibility (especially those wires!) before I open it up.