Random hard shifting (UNRESOLVED, Goes away after restart)
 

Today I drove downstate about 200 miles. The car acted fine during most of the way, then when we got off the expressway, the car started shifting hard, like an ultra firm quick shift, not the good kind. So we went to do stuff and parked for an hour. We got back, the car shifted fine, then it started acting up again. We went to eat for abotu 45 mins, after wards, the problem was gone. Normally, the transmission shifts like brand new. It did this once before randomly for about five mins of driving. Then later that day, it was fine, so this leads me to think it's not a mechanical issue with the tranny. THE FLUID IS IN GREAT CONDITION! It's a bit overfilled though, but never causes problems any other time.

Another thing, may be related. The temp always stays around 180*, but it got up to about 200* today on this trip, then it fluctuated between 180 and 200, and I think that might be related?

Also, after long drives of 70-80mph, the oil pressure will drop to about 25psi, and then it seems to be fine after shutting the car off for a few mins.

This is only on trips. At home in my town I do constant stop and go, and I never have a problem. Any Ideas?

EDIT: I went on a trip about 90 mi or so, and the tranny just out of nowhere started shifting hard again. I pulled over, shut the car off for like one minute, and then it was fine the rest of the way home (another 60mi), PCM issue? Also, the fluid on the dipstick indicates it to be FAR higher than normal!

oh, and no codes were thrown

There's stop and go traffic in Tawas?!?! :lol:

This occassionaly happens to our 99 as well - real hard shifting after a long highway drive. It has never thrown a code, and I never put much thought into it.

As for the low oil pressure, you should hook up a mechanical oil pressure guage. You could have two seperate issues here.

Most likely it's the TCC acting up. If it fully goes bad the usual failure on a TCC is to stay locked all the time.

yeah the jerky shifting has only happened like twice since I've had the car (9mos), it happens 1-2, 2-3, and 3-4, whether the shifter is set at "3" or "D"

I had to hit the gas pretty hard earlier that day when merging on the expressway, it seemed like after that is when it started shifting rough, but liek I said, only for a time, then it completely went back to normal. I think the trans must have gotton too hot?

http://www.bonnevilleclub.com/forum/...ight=A&start=0

This is Exactly my problem. So a tranny cooler might help?

My 99 started having hard upshifts a couple of months ago and finally set a code of P0741 (TCC Off). It was time for state inspection and they couldn't complete it due to MIL being on. Took it to tranny shop, after troubleshooting, declared pump shot and a bad solenoid. Tranny rebuilt to a tune of $2K. It has been back in shop three times and going in for fourth time tomorrow. I don't know if the shop doesn't understand GM trannys or they're having a run of bad luck, but I'm ready to scream. Today it drove worse than original and set a P0742 code (TCC On). I'm glad I have my 76 Vette as back-up. Between the UIM, LIM and the tranny, I'm hating GM a bit. :evil:

bump

:D Got the Bonnie back from the tranny guy Thursday, shifting is like new, TC lock up is right on, I'm a happy camper. The fourth try involved another tranny completely, this was an expensive job for the guy, but that's the business. The next few guys will probably be payong more than usual. One thing I didn't like to see was the tranny fluid level, it was about 2 qts overfilled. I gotta put that to the tranny guy, doesn't seem right :!: