I searched and didn't see this issue mentioned. On my son's 92 Z28, all the gauges and tach work correctly, but as soon as you put the car in gear the speedometer starts climbing, even with the car not moving. Normally it goes to about 30 MPH and stays there when the car is sitting, but then if it starts moving it climbs again and doesn't stop until it either pegs out, or the car is shut off.

Would this be in the cluster, the VSS, the buffer, the ECM, or a ground that isn't grounded?

The car is a stock 92 Z28, with the TPI 5.7, 700R4 automatic. To my knowledge the transmission hasn't been out of the car.

Just looking for a place to start looking.

 

Maybe all you need to do is pull the speedometer out of the cluster and re-seat it. There is no cable to mess with for the 90-92 clusters. Mine has done funny things before, mostly not deflect at all, and that's all I had to do. IIRC, there are 4 pins in the gauge pod for the speedometer - I don't have mine any more for reference.

 

Thanks, I'll give that a try. I also have another cluster that I'll try. I have a pinout diagram for the connections, so I'll run some tests and see if all of them are showing what they should be showing.

 

Okay, swapped instrument clusters, same behavior so I put back in the 140mph cluster. A few questions.

1. Does a 92 Z28 with the 5.7 have a VSS Buffer box?
2. Does the VSS on the transmission go off a gear or a tone wheel? I pulled the VSS out and the transmission that's in the car currently has a tone wheel and sensor and not a gear driven sensor.
3. If it's supposed to be gear driven, is there any way to get the tone wheel sensor that I currently have work, or do I need to change the tail shaft or transmission?

Also, if anyone has a picture of the correct VSS sensor out of a 92 5.7 it would be appreciated.

Thanks,
Scott

 

Here is what the VSS looks like that I pulled out. It looks like it's from a 93 c1500 truck. Any way to get this to work with the stock 92 ecm and cluster?

 

Okay, so it is a tranny out of a truck from what I can tell, and I'm going to try to put a DRAC from a 95 silverado in to get the correct signals to the speedometer and the ecm. I'll provide an update when I get everything sorted out.