I posted this on the general forum, and the only response I got was to try here .... Recently I noticed my speedo doing something odd. When I am on the gas, it works properly, but when I back off the gas it immediately drops. At 30mph it drops to 20; at 40 it drops to 25, at 50 it drops to 30; at 60 it drops to 35. If I put the car in neutral, it drops a little, but it drops the most when in gear and I lift the throttle. The car is NOT slowing down like that; my relative distance to other cars doesn't change. Anyone have any idea to fix this?

 

The Vehicle Speed Sensor installed on the transaxle. The part inside the transaxle has a plastic gear which is driven by the internal parts of the transaxle. The part outside is a signal generator which produces a square wave of amplitude 5.2 volts and frequency proportional to vehicle speed.

The signal from the VSS is used for several purposes including driving the speedometer. Perhaps your VSS has a loose connector or a damaged wire in its harness. The engine and transmission are supported by flexible mounts and some motion while driving is normal. That motion may be making and breaking a loose connection.

Remove the VSS, attach a voltmeter to the electric leads, and spin the gear by hand. If you get zero volts, it's dead.

One owner discovered his VSS was not fully seated in the transaxle. He just tapped it inward, and retightened the 10mm mounting bolt.

For more information please refer to the Chilton repair manual (page 4-22) or the Haynes repair manual (page 6-16).

 

I recently had a broken axle replaced. I wonder if the problem you describe could be a result of the work that was done? Thanks for the tip on what to check. It could just be loose.