I recently did a 300 mile trip and I noticed that my trans occasionally jumps out of OD and into 3rd with the cruise on or manual throttle. Fluid level is fine and color is blood red. No burning smell. Any ideas?

does this happen at a steady speed on flat ground, or were you approaching a slight hill at the time it dropped down to 3rd. It may not be really dropping out of 3rd it may be kicking out of TC lock up, can make it seem like it shifted because the rpms will go up.

I am no expert on the transmission stuff, but we won't be able to help much until you tell us more about what conditions (hill?) you had at the time.

slipping. bands may finally be worn out. If as such is the case, rebuild. 1600 USD is what that normally costs. Any codes? Any abnormal behavior at acceleration or decel? How many miles? Have you rebuilt before, or has any rebuild been done to the best of your knowledge? What year? Have you checked your vacuum lines/fittings (if applicable)?

No rebuilds, 140K (thousand miles). I noticed it on a flat surface under steady speed. But as I said it's not constant. Yes the tach does increase as engine speed increases.

what speed do you drive?

how do you check fluid level?

the speed question, believe it or not, is an important one.

speed between 55 and 65 mph. Noticed it's usually when I'm between 45 and 55 mph. I check fluid level hot in nuetral on level surface. if it helps.

if its around 45mph the car is going to do that. Mine always has.

Drop the gear selector into 3rd if youre going to be cruising at that speed.

your trans may just not be satisfied with the rpm vs load vs mph and trying to compensate by either unlocking the TC or shifting to 3rd. between 45 and 55 it probably prefers 3rd if there is ANY change in the throttle position.

I noticed you have a 2000 SE is that the 3.8 or 3.1 in there?

I wouldn't expect it to do that around 65 or 70 unless you were on an incline or got into the pedal more.

I am taking this at a PCM standpoint, and richard is going towards the mechanical. so maybe we will meet in the middle on something.

check fluid as such:
run car until engine and tranny reach operating temperature. Ensure engagement into various gears, including reverse.

allow to rest on flat, level surface for 5 minutes. Check fluid level, wipe dipstick clean, check fluid again.

continue on with remainder of day already in progress.

The speeds that you mentioned are known to be problematic for these cars. Those RPMs/speeds are right in between certain shift points and are known to cause intermittent symptoms similar to slipping clutch bands. If you dont notice metal flakes (Aviation calls them "chips"), no burning, and no other symptoms, I would say there are no issues with the tranny. My recommendation would be to get the car cruising up at 65-80 MPH and see what the vehicle does then. If you do have anywhere you CAN cruise that fast. Out west, those speeds are an everyday kinda thing.

Your a Pontiac shop forman and your asking this question?Between 45-55 these cars have a problem with gear hunting ,an easy remedie is to keep it in 3rd gear under 60 .Chico(pops)

My ZZP PCM cured that

Chico..You knucklehead, lol I am the Detail Shop Foreman. And besides I quit there 3 months ago. For some dumb reason Chrysler pays better. That aside...I'd absolutely love to cruise my car at 85, even 185. Just nowhere to do it. I seem to remember the same issue with a certain 2.5 Celebrity I had many years ago. But the 2.8 in the Eurosport after that didn't do it. I know my car has some big miles on it and I just wanted to assure that it wasn't gonna get smoked on a roadtrip.

Oh yeah last answer. It's a 3.1 Does the ZZP Pcm work with this engine or is having the 3.1 setting up for suicide?

I don't know why they threw a 3.1 in these tanks.

I don't think the 3.1 guys get better fuel mileage, maybe I am wrong, but its a heavy car it needs the 3.8.

I don't think they make a pcm for the 3.1, so that leaves you with suicide... J/k.

anyway, if all it does is downshift between 45 and 55 an no other issues. then there is nothing to worry about, its just being a grand prix.

and you said chrysler pays better? so when GM buys chrysler, will your pay get docked? (i haven't followed up on the deal, so I don't even know if it is still going to happen, lol.)