1990 GXE auto
Kind of strange thing happening.
The speedo, when driving, goes up to 35mph and just stays there.
When I stop, it will go down to 5mph.
It runs and shifts fine.
I'm thinking a bad ground wire to the dash.
Everything else is working fine.
Anyone else had this problem???
Suggestions???

 

Since no replies, I'm guessing not a common problem.

I checked the sensor.
It puts out voltage when I can spin it fast enough.
So it looks like it's working.
I left it disconnected, and the speedo didn't work at all.
Plugged it back in, and same problem.
Going to have to pull the panel out next.

 

Unless the voltage plateaus when rotating the sensor, it's likely going to be the speedometer itself.

 

It has to be spun fast to get anything out of the sensor.
Can't keep it spinning at a constant speed for long.
I wound a string around the gear, and pulled, that spun it fast enough to get a reading.
I'll just have to pull the panel out and look if I can see anything.
Do some testing of the circuit.

 

You can remove the pinion temporarily and run it with a drill for testing.