The PO of our 93 Breakaway had the speedometer stop working about 1000 miles before he turned it over to us. He thinks that it is the sensor. The needle will sometimes be still and other times go erratic. Bumps and wet weather seem to make it more erratic. He thinks its the sensor on the Allison Tranny. Can anyone tell me where the sensor is located? Thanks
Jim

Did the odometer work at all?

I have a problem with my speedometer, if after a long period of inactivity, I turn it on and the speedometer will start to read about 15 to 20 MPH and then read about 10-20 MPH higher than actual speed. it will wonder around a bit and after about 3-4 hours it will start to settle down and finally be OK for the rest of the time.

The odometer on mine works OK and is accurate.

Although I have a GM system, I've had a similar issue a couple of times - pulling the transmission connector, drying with acetone, then cleaning the contacts, cured the problem - but it took a couple of times before the fix became permanent.

That is why I asked if the odometer was still working. If it is, then the sensor is OK and the internal speed display circuit has a problem.

This intermittent and erratic speed readings are a common defect of the early '90s VDO speedometer according to the speedometer shop I go to.

If mine gets to bad or does not settle down I will have them take off the bezzle and I will try to trouble shoot/repair the unit. I want to keep the white pointers.

In the Breakaway, the speedometer will be eratic, one moment at '0' and the next at 30mph. When it is at '0', the odometer is not working. When the speedometer is bouncing around, the odometer will click away, even if the coach is standing still.
Sensor? Where might it be on the tranny?

This sounds like the type of problem Rusty fixed by cleaning the connections at the sensor. This is NOT the same problem as mine.

Look for the sensor around the drive shaft end of the transmission. It should be a small screw-in device that has a connector at the end of it.

It should be close to the output shaft, certainly in the rear housing of the transission

Actually, my odometer worked although the speedometer didn't. But as Ed points out, mine isn't VDO.