I have a 95 f15 351w e4od. This morning the ABS light came on, the speedometer is dancing wildly and the transmission is not shifting right. Where do I start? Does the speedometer get its count from the sensore on top of the rear diferental?
X3...check for codes. Very rarely does the VSS go bad. We have seen many folks on this forum replace the VSS only to find they have the same issue. It is advisable to remove the VSS to inspect it and clean it off then re-install. Drive the vehicle to see if the issue is resolved.
If you still have the problem it's time to breakout the meter to measure the VSS signal at the input to the PSOM behind the dash. Subford has also mentioned there is a RABS test harness located on the driver side firewall. The VSS signal goes to the RABS control module, located behind the glovebox, on it's way to the PSOM. You can place your meter there too. The test is to jack up the rear axle, after blocking the front wheels, running the truck up to an indicated ~30MPH while watching the meter. The voltage should smoothly rise to approximately 3.5 Volts. If the voltage is low, try disconnecting the RABS control module connector then re-run the test. More often than not the RABS controller is bad which causes the VSS signal to be pulled down.
For me there is, "to much air space in between the Ring Gear and the VSS sensor and also worn // chips of metal taken out of the ring gear.
This could be caused by old age and also not shimming up the gears properly. I did 3:55 to 4:10 swap back in 2001 by my self at the age of 17. Since then I'v noticed some slop forming in rear-end when I accelerate and let off the gas. So it's almost time for a rebuild.