I have a 1992 Chevy Cheyenne C1500, 4.3L, 5spd M, 2WD, Standard cab. I just had a new clutch assembly installed and freeze plugs replaced. The engine had to be pulled to get to all the freeze plugs. When I got the truck back, I noticed the speedometer along with the oil pressure gauge would move up. Mostly the speedometer. It acted like a tach when sitting still and revving up the motor. Also when driving down the road, the speedometer would show I was going 80-85 when I was actually going 45. Has anyone had this problem and if so, was the issue found and resolved? I checked all the ground wires and cables. (Battery to block and block to chassis.) Cleaned all connections down to bare metal just to make sure.


Thanks

 

Ok. I've added a video of what my speedometer is doing. It's only about 20 seconds. Any advice?
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Speedometer issues - YouTube