No OD, or Speedo

[moparnut426]

I have a 91.5 intercooled W250. Has cruise, Auto, 4x4. When it sets overnight recently, the speedo stops working, and the OD wont kick inn. Cruise dosnt work when speedo is no either. Ive noticed if I drive it some distance, and hit a decent bump, then it will start to work, and everything is fine. Now I replaced the VSS, and it still isnt working. I dont have any ABS, or Brake lights coming on, and everything else seems fine. Ive tested cotinuity on the black with blue tracer, and the white with orange tracer wires as far up the tranny as I can reach and they seem ok. Now the black with Blue tracer has cotinuity with ground. Is that correct?? or is that my issue? Can the SBEC be the issue? I raised the truck off the ground, and put it in drive, and the square drive gear is turning and spinning the VSS, so That is ok there.

Any sujjestions would be great.

Kasey

[josh_6bt]

try unplugging the connector at the VSS and rotating the speedo adapter to a different spot. Worked for me.

[moparnut426]

Ive done that, and nadda

Kasey

[peobryant]

Do you ever have the speedo working but no OD? The TPS may be to blame for no OD.

[moparnut426]

One time I had spedo and no OD, but then I hit a nasty bump on these Nebraska roads, and it kicked on. I can check that.

Kasey

[Mark Nixon]

Prochaska, it's an Intermittent VSS or bad TPS.
The TPS controls speedo function as well as the overdrive and cruise.
Lose it and you're using your foot, blind and slow.
USUALLY it doesn't take out the speedo, just the cruise and O/D.

Lose the VSS and the same things occur, ALL of it.

CHECK THE WIRING, FROM THE TRANNY TO GREY/BLACK ENGINE CONNECTORS, many times these have chafed and are either cut, or are exposed and grounded.

It can also be the control module on the fender, but most of these troubles are usually related to the wear items.

If it's the TPS, you might as well do the potentiometer fix, because a new TPS for '91-1/2 to '93 is well over $200.

Mark.