ok. Driving my van (96 b2500) and the speedometer is jumping all over the place. Once I hit about 70, everything is okay.
then I feel the van kind of drop gear and then shift back again, all within a second. At the same time I notice the speedometer has jumped down to 60,then after the shift back to 70.
​​​​​​Happened a few times on the drive. Is this a related issue or is it a transmission problem?

 

Likely the VSS (vehicle speed sensor) is having some issues. If the pcm sees vehicle speed jumping around, it will be confused about which gear it thinks it should be in. VSS is on the tailhousing of the trans, may wanna pull it, and inspect the gears. (yes, it is gear driven on the 96. )

 

thanks. have a couple of long road trips coming up and would hate to have an iswsue on the road. is this something i can do myslef? or should i take it in? i reall yno nothing about cars, but i have read this haynes manual, which has helped me do a a couple of small things.

 

It is relatively easy. It's one bolt, and a wiring connector. Take note of how the VSS is indexed in the trans housing though. It will only go in one way, and actually work right.

 

thanks!! looks like i have a project tomorrow morning. i should probably not drive the van around at all until its fixed, should I?

 

If you have something else to drive, leaving the van parked till its fixed isn't a bad idea.

 

well, i replaced the VSS, pretty easy. drove home from work tonight and the speedpometer still jumps around a little. not like before, but a little. so thats good. going to drive it tomorrow before i head out of town and see what happens when i hit 60-70.
what else could it be?

 

Maybe a bad connection somewhere? Would be interesting to see if the PCM is getting the same erratic readings, or if it is just the cluster having an issue..... however, I don't know if the scanner would react fast enough to actually show anything.....

 

Does yours need to be rotated to get it into the correct position? On the 1991 the positions must be related to the diameter of the gear (# of teeth). You may need to pick 1 position more to get the correct tooth engagement.
Steve

 

i rotated until it would fit in.