I have a 91 RS and this morning on my way to work my speedometer quit working. I noticed it while I was on the interstate at speed. Then it began to work intermittantly at best. Once I got off the interstate and slowed to under 40 mph it was working. Any ideas on what may be causing this? I only drive the once or twice a week and I'm about to strip the interior out and replace it. If I have to do some work on the guage cluster this is most likely when I would tackle it. Any help would be great!

 

The speedo in my bird does the same thing every once in a while. Usually in the morning it just stays at 0 while I'm driving. When I give it a good "whack" with the back of my hand between the tach and speedo it jumps right up to where it's supposed to be and usually acts right for the rest of the day. I know this isn't a fix, but if it works on yours at least you'll know how fast you're going.

 

You have a bad ground somewhere in the speedo circuitry. It could be in the dash itself, or somewhere in the wires going from the electronic speedo on the transmission, to the dash. Good luck finding it.

 

yea damn grounds : ( always causing probs

 

what i would check first would be the gauge connection. i had a problem like this a few weeks ago after a dash swap and it was the left connector (closest to the driver door). if you take out the gauge trim piece and reach behind there and play with that connection you would be able to tell if this is the problem, of course you would have to do this while driving, which wouldnt be too hard. i also har problems with the fuel gauge and oil pressure gauge at the same time however.

i dont know if this will help but hopefully so

 

700R4 uses a speedometer cable,it attaches to the back of the gauge cluster and to a plastic gear in the tranny. Could be the cable, or the gear. To check the cable, pull the gauge cluster (not too hard) and look at the end of the cable. It should be square, if it is rounded (would act up like you mentioned) it needs to be replaced. If it is the gear in the tranny, it will go out all at once and will not be intermitten.

 

my spedo is 10 mph off at 70, ill be doing 60 but my wife will be next to me and it says 70, how would this be fixed?? stock rear

 

If you change tire sizes you need to change the speedo gear.

 

Thanks for all of the input and ideas. I believe that I will follow up on Auto Missions idea since I have never had the dash apart. The cable is probably just worn out due to age and use.

 

I agree with Auto Mission. I had a similar problem, my speedo wouldn't work at all and then when I hit a bump, it would jump around for a second or two and quit. I found that the problem was the gear on the end of the speedo cable that goes into the transmission. When you take it out of the transmission, if the teeth are worn down, you know thats the problem.

A new gear from GM cost me $45 and you can only get it from GM.

 

There is no speedo cable on 90+ Camaros and 86+ Firebirds. They're all electronic. The speedo drive gear on the output shaft of the transmission is the same, but the speedo driven gear on the speed sensor unit in the tailshaft is different on cable vs electronic speedos.

 

Then it sounds like the speed sensor is going out.

 

Thanks, I stand corrected.

 

Everything is stock ^^