OT- 98 Chev truck transmission question
 

I've got a 98 Chev 1 ton dually w/ 454
Ocasionaly after towing, after I drop the boat, if I drive without towing, the trans will shift real hard, untill the truck is shut off and cools down..then its back to normal.
One trans shop said that 98-99 GM trucks had problems with the engine distributer wearing and screwing up the signal?? to the trans at right around my milage. Since he's turning away business, I tend to belive him. Has anyone else experienced this. The trans has always been serviced regular(just done) and has 90K miles on it.
Does anyone know a message board for Chev trucks info??
Thanks
Dan

I have the same tranny and I programmed it to shift firmer. I agree it does shift diff at different times but it doesn't feel bad. There is a temp sensor in the tranny. Maybe it shifts firmer when hot to generate less heat from slippage.Just a thought.

low voltage will cause the same symptoms:)

Its not a bad idea to run a trans temperture guage on a bigger truck pulling a big load. If you see tranny tempertures at or above 260-270 degrees you should install a bigger transmission cooler in line with the factory cooler and consider a deep sump tranny pan. Hot tranny tempertures can cause tranny valves and parts to stick and hang up, which can cause hard shifts when its still to hot.
Raylar;)

Turned out the trans is fine. It was the TPS (throttle position sensor) cause it to shift hard.
Thanks for the input.

Dan

These trans control system has a "learning" mode where line pressure is increased under heavy loads or high speed driving in order to minimize slip and reduce heat . Although most drivers probably don't notice it, espesh those that don't pull trailers, it's fairly common.

If there were no other drivability problems, I would be surprised that the TPS was the culprit. I'd be curious to know how it works again under similar driving conditions.

JJ

Ran it this weekend w/wo load...all is well.:D

Dan