shifting problems

[sweet93]

i have a 1993 gmc sierra 2wd. the problem is when i go over bumps or any kind of jolt the truck gets it drops down from overdrive to 3rd then back to overdrive. i was thinking it may be the transmission control module but i cleanned that conection and it fits tight. i dont know what else it could be. maybe the ecm?

 

[Tempted]

You sure its dropping into third and not just unlocking? When you hit a bump you generally lessen up on the throttle pedal. When you lessen up on the throttle pedal the converter will unlock, raising your RPMs without dropping down a gear. Next time you are driving at a constant speed, touch the brake pedal while keeping a steady foot on the throttle. The RPMs will raise but the truck isn't down shifting.

 

[sweet93]

thank you tempted for the response, but yes it is shifting. i can feel it when it does it. it does it when im riding really low most of the time. the truck is bagged and body dropped.a couple of times it would do it back to back, like there is some kind of short. i just had the tranny rebuilt and gone through. the first time this happened i was driving then i went over a bump and 3rd and overdrive wouldnt engage at all. then i had the tranny rebuilt to have the same problem. then he wiggled some wires behind my glove box and then it worked. i replaced the white box but it still does the shifting down then back up like it looses power to the over drive module. im very confused

 

[Tempted]

Got me, I'd have to look at it. It could very well be the linkage. At full drop you might be torquing it. Could cause it to drop into 3rd.