I purchased an 87 T/A gta a few months ago and just had the digital dash replaced with a new cluster. It all looks great and everything that wasmt working now is, except the speedometer. It was working before now it will raise up to 13mph then jump to 23 then drop to 0 and remain there. Im not the most technical with this stuff but my best guess is something isnt connected right? Any help would be appreciated

 

Dang, was hoping someone had replied to this. I'm def not the one to help you because I'm a medical idiot... I recently bought a 1988 Camaro and my spedo has an issue as well. Mine is mechanical... it bounces around and seems to be about 20 mph off... from what little knowledge I have I'm guessing my problem is either with the speedometer cable or the speed sensor.