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Speedometer/Odometer Problems

MrTruck805

MrTruck805

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Hi All,

The other day I replaced the busted speedometer/odometer cluster on my 89 Jimmy with a supposedly working one from ebay. The install is quite simple, just the cable that comes from the back of the transmission/transfer case area, and a green/red two wire connector that should go to the ECM I assume. After putting it in, neither the odometer or speedometer works, and I get OBD 1 check engine code 24 (Vehicle speed sensor error).

I just did some searching on the forums, and some people mentioned the numbers on the odometer can lock up and to spray some lubricant in there. I haven't tried that yet, but I will. Also, before putting it in I spun the back part of it and verified that the speedometer did rotate. Any other ideas on how to debug? Junkyards/Pick and Pull isn't an option here unfortunately.

Thanks!
 
I'd double check to see if the cable is spinning properly. You can then also lube it while you have it exposed (lube can be picked up at auto parts store).

I would pull your cluster out and then drive around to be sure the cable is indeed spinning while you move around. If not, check your t-case connection.

Once that is verified, be sure you connect it to the speedo nice and solid. There is a clip on the back side that will snap once you get it seated properly. Then drive around again to be sure you get your speedo/odometer to work.

Finally, there should be an "eye" on the speedo which is the green and red wires. That should go into a green box and then send a signal to your ecm and cruise.
 
Thanks for the reply. Speedo and Odometer are now working!

I pulled the cable within the cable out with some needlenose then stuck it into the speedometer receiver part to make sure the connection was good, and then put the clip in. Threw some lube in for good measure, and we got a working speedometer and odometer. Not that I could speed in it anyway, but now I can accurately see how slow I'm going.
 
If I have an odometer that doesn't work...in my case it seems to be stuck. When I push the button to reset it just sticks and won't budge. How would I go about getting it functioning properly?
 
What year are we talking about? I'm assuming you have a mechanical speedo?

Big G said:
If I have an odometer that doesn't work...in my case it seems to be stuck. When I push the button to reset it just sticks and won't budge. How would I go about getting it functioning properly?
Click to expand...
 
FYI, 90 & 91 trucks have an electric speedo.
 
I could help you out with some suggestions if you were mechanical, but I would start your own thread asking for help for an electric one. I'm sure you'll get a lot of good suggestions on how to best troubleshoot. This site has never let me down.

Big G said:
ok...all I know is it doesn't work...:dunno:
Click to expand...
 
I'm 99% sure my 1990 is mechanical. (Th400/205) mine works, just reads slow/erratic/bounces around.
 
The problem with my 89 mechanical speedo being slow and erratic like yours was a poor connection between the plastic end of the cable within the cable that rotates, and the speedo cluster. I connected it and clamped it many times, only to have the connection get worse as I drove it. What I ended up doing sounds dumb, but has worked perfectly since I did it. After connecting the plastic tip of the cable to the cluster I wrapped what was left of the plastic tip in duck tape so the connection inside the other cable would be a little tighter.

I know I didn't explain that well, but it worked perfect for me. Here's a pic of the plastic part I was talking about.

speedo.JPG
 
I downloaded a speedometer app for my phone. That and Google maps confirmed my speedometer is 30% off. At an indicated 45 I am going 60. My tires are taller than stock, but not but not enough to cause a 30% deficiency. And at low speed it bounces, according to GM if the speedo bounces at low speed it is shot and needs to be replaced.
 
Mine was bouncing a little at all speeds. I found that the cable was coming apart inside the speedo gear housing in the t-case. That cable is like one spring wound around another one and the outer one had unraveled into a mess at the end. Fixed that and the bouncing stopped (now the cruise works OK again) and the repeatability improved. (Before that I could see like +/- 5MPH for a given GPS speed).

If you are off by 30%, the differential gearing has likely changed. Maybe somebody swapped axles or changed gears. Hopefully there is a driven speedo gear with enough teeth to correct it.
 
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