2 replies to this topic

[kolathwi]

Hello,

My 94 GV when coming to a stop will surge or jump when shifting down to first. I don't know if this is the famous "bump shift". I changed and flushed the fluid (ATF 3) and didn't see any improvement. Any thing else I should take a look at ? Do I need to have the TCU reset?

Thanks.

[domer]

I'm quessing you have a 3.3,3.8???? Then you would have a TCM, could be convertor that is holding lock-up to long or a pressure problem inside. Need to have someone look at CVI(Clutch volume indexs) to see if there is a pressure problem. A number of things could cause what you have, and most aren't simple, sorry. Good luck.

[malcom]

The bump stop occurs when you stop and then on an immediate startup the transmission will clunk or bump as it goes into gear. It happens on startup not slowdown.

The Throttle Position Sensor on the throttle body can cause this. The TPS sends a signal to the transmission on when and how hard to shift. If it is worn out, the tranny may think you want to accelerate when you actually want to stop. About $20. It has been revised since your van was built.

Also, I hope you have a revised TCM (tranny control module). Check for stickers with dates on it. The TCM is a rectangular box on the passenger side firewall with a large multi-wire connector on it. The new software improves the shifting and longevity of the tranny and stops the bump stop. Dealer may be able to reprogram but look for a used one such as on EBAY.

Try cheap simple fixes before you go to a shop. They always say you need a new transmission.

Edited by malcom, September 15, 2004 at 04:38 pm.