Hey guys, I have been expericening an intermitent transmission problem where the OD light is flashing and then the shifting is really late and hard in first gear and too fast through the other gears. I tried some other solutions with no ultimate fix. I got a code reader and hooked it up after getting the problem again the other day. Code 29 came up, so I took the VSS out and wiped it off but then got the problematic shifting again last afternoon. The funny thing about this problem is it never happens in the morning when its cool, always on these hot afternoons when the truck has been sitting in the sun. Maybe a conencidence, but I have notice the pattern. I bought a VSS last night but haven't installed it. Could it be the other problem related to code 29? Something with the speedometer maybe? Could it be something else with the rear end, maybe need a fluid change or something? The VSS was only like 12 bucks so I just figured put it in and see what happens. The hot temp on the inside of the truck makes me think something with the speedometer could be at fault. Another note is that one time before it happened I noticed my speedometer bouncing a little but only above 60 mph and it seems to still be doing that, maybe I just never notice before. Please Help!

 

ATSG states:

Erratic shifts
BAD VSS
Can cause erratic shifts and LU problems. May not set code 29/452(VSS speed sensor signal to low).

Note
VSS is located in transmission tail housing or differential

To check VSS

1. Remove 2-wire connector end.
2. Hook DVOM meter to pins on sensor. It doesn't matter which way you hook it up.
3. Set scale to AC voltage/ 0 to 40 volt scale.
4. Raise vehicle so rear wheels are off ground. (I would do this out side and chock the front wheels)
5. Start vehicle, put in 'D' and make transmission upshift. Watch meter. ( I would recommend using 2 people here. One to control car the other to watch meter.)
6. You must see an increase in AC voltage or VSS is bad.


Hope this helps.