Transmission Hard Shifts

Hello!

I have a 98 Trans Port with about 160,000 kms on it. Sometimes, when I am accelerating, it shifts VERY hard, almost a "clunk". This is not dependant on hot or cold running. If I shut the engine off for a few minutes then go again, it stays gone!
I have changed filter and fluid. I have tried running it in 1st and 2nd hard to clear any blockages. When I downshift to pass, or decelerate, it does not shift hard, only from 1st - 12nd - 3rd - overdrive.
Any thoughts??
Thanks in advance.

Shane

Further to last - this is very intermittant - not every day.

Have the 1-2 shift solenoid checked and replaced. It sounds like it is sticking and causing your problem. Once it does this it probably clears itself and works properly. You should be able to change this yourself as they are not hard to change. Check other threads on the Pontiac forum and you will probably find similar problems.

Thanks! I will give that a try.

,,,and also, the manual says 1-2 accumulator sticky, as an alternate...By the way, in this tranmission, it is normal hard shifts occur only when going up..because this is the time a new clutch engages in addition to others for each succeessive shift, (this is the beauty of the hydra-matic design: there is no possibility of overlapping clutch and band like in fords and chryslers)...when going down, clutches simply open one after another, thus no hard shift possible.

thanks! If it is sticky - is it possible to service? (clean)

I did not so it...but from the book, it shows as a serviceable item: just have to remove the transmission pan. The whole accumoplator and servo can be taken out and serviced on the table. Lots of O rings and little springs....I'll scan these 2 or 3 pages and post them later to nite www.avigex.ca/xport/servo1.jpg
www.avigex.ca/xport/servo2.jpg
www.avigex.ca/xport/servo3.jpg

you rock! Thanks!

none of your links seem to work for me????

um - they still don't seem to work - just a box with a red X in the middle...

Internet explorer opens them in the browser without problem...or you can download the file using the right mouse button and open then with "paint" or better, ms photo editor.
You can see the index of documents at:
www.avigex.ca/xport
If you still have problem, I may e-mail them direct to your e-mail address.

i was able to get servo1 and servo3 pics - servo2 did and does not seem to want to work for me! If you would not mind - could you please email servo2 to me at [email protected] ?? thanks! btw - what does LMP stand for? London Motor Products??

I have this exact same problem.
i notice it after the van has driven over 30min or so.
when its cold i never see this problem. once it warms up it is there. BTW i put the largest tranny oil cooler i could find onto this vehicle when i bought it. my lsat van went through three trannies then i junked it.
Is this for sure the problem? What would a repair like that go for?

Hello!

I have a 98 Trans Port with about 160,000 kms on it. Sometimes, when I am accelerating, it shifts VERY hard, almost a "clunk". This is not dependant on hot or cold running. If I shut the engine off for a few minutes then go again, it stays gone!
I have changed filter and fluid. I have tried running it in 1st and 2nd hard to clear any blockages. When I downshift to pass, or decelerate, it does not shift hard, only from 1st - 12nd - 3rd - overdrive.
Any thoughts??
Thanks in advance.

Shane

I`ve got the same Problem on my 99 Chevrolet Transsport ( 150000 km). Have you got any Ideas for a solution.
thanks

yeah, do what i'm going to do.
Never buy a GM product again....
I contacted GM on this and a few others.... (roof rusted through!)
THey were very unsympathetic. basically tough titty
Well GM, I was a loyal customer. you have burned me for the last time.....