Digital Speedo at Zero

[gregsmyth]

I have a 1991 Buick Regal Custom with the digital speedometer. One day while driving 65 mph, it began counting down to zero, and never got above 2-3 mph after that. After three days it has been stuck at zero. For months before this, it wandered up and down, but never more than three or four mph, and very intermittantly.
The Haynes manual does not mention the digital dash, sending unit/sensor, or even the wiring of the thing.
What should I check, and where is it located?

 

[Syndicated]

this problem sounds like a broken speed sensor gear. The gear on the speed sensor sits on the output shaft of your transmission and since it's made of plastic, the gear is prone to breakage. What you need to do first is pull the old one out and check which colour the gear is before you can get a new one. The easiest way to do this is to get under the car and look at the transmission. Look at where the passenger side axle shaft goes into the tranny. On top of the transmission in that area you'll find a wiring harness going into your speed sensor and a 10mm bolt which holds the speed sensor down. You need to remove the bolt first and slide the sensor out. It may seem like it's stuck, so try to twist it back and forth to break up the corrosion, and it will slide out. Then unplug the wiring and go get a new one. If all the teeth are broken off the gear, then you'll probably need to bring your VIN to the dealer so they can find the right part for you.
Installation is pretty much the reverse of removal except sometimes it's hard to know if the new sensor is installed all the way, there should be a metal tab which will sit more or less flush against the trans case, throw your bolt in and tighten it snugly. Too tight and you'll strip the aluminum threads in the tranny.
I hope this helps!
If you have any more questions, email me at bvollans@cogeco.ca