Hey guys. New here. I just bought a 91 trans am, and the speedometer appears to be off. I know I'm going faster than it says, lol. Also the odometer and trip miles don't track. Is this related? Has anyone seen this? Anyone know how to fix?

 

It could be a number of problems. Maybe there are different size tires on there then stock (which wouldn't be noticeable really). Maybe the guys before you put different gears in the diff which could cause that. could be a faulty sensor.... I believe those are electronically controlled speedometers. The trany gears could be different. maybe there was a trany swap done on the car at some point. Start by taking the diff cover off and find out what gears are in there and see what came stock on the car. that is the easiest thing to try first.

 

As far as the speedo being off, chances are you either have the wrong wheel/tire size, or someone has changed the rear-end gear ratio.

As far as the odometer and trip meter not working, they run off the same chintzy brittle plastic gear, and they frequently don't work in these cars. The trip meter/odo in my Camaro works occasionally when it can find a tooth in the gear to grab onto, but only at highway speeds, and never for more than a few miles.

Best bet for the odo/trip meter is to remove the cluster and have a electronics/gauge shop rebuild it. There is no good known fix for your year; closest thing I've seen is a 3D printed replacement, but apparently they don't fit: https://www.thirdgen.org/forums/afte...-odometer.html