Ok, I've done alot of driving in the past month and I'm starting to feel random long shifts. It doesn't happen in the same gear. Happens mostly when I have the A/C on (under stress), but still does it when its off every now and then.

Is there any specific solenoid that usually goes bad I could change to fix the symptom? If I do change out the sensors/solenoids...where are they and can I do them myself, or have to take it to a mechanic?

It has had a trans service before I got the car, only 18,000 miles since. I may change it again since it was its first.

 

When you say the trans was "serviced", I assume a fluid drain? Pan drop and filter change or just a hook up to a flushing machine?
I recommend strictly a pan drop and filter change. If that was not done when it was serviced, I suggest doing so. Also, some re-use the pan gasket (I never have, I change fluid typically at 100,000 miles with some exceptions). From what I can tell the gaskets are marketed as re-usable (and have a nice metal core), but I have yet to see one I trust to re-use. That being said, I have bought the re-usable ones via RockAuto and I think it changed me for life with trans fluid changes. So much easier then the ol' freebie gasket with the filter and I am sure a longer/more reliable life. And even though it's re-usable, I don't plan on ever re-using it. It's rubber coated steel, after all the hot/cold the car goes through, the rubber does wear out.

Anycase, back to your shifting, a pan drop/fluid/filter change might be the best first step. I do no the 4T65E and 4T65E-HD trans have histories of breaking down. If mine ever does, I am probably going to look to Triple Edge Performance.

And some of the shift issues may be in the factory tuning somewhere...

 

the dealership that had the car when I bought it did a service, filter and all the normal stuff. I was there and watched them do it.

I just find it so strange that its at random shifts, not the same one, and not all the time. I know what they feel like when they go bad experienced it in my bonneville before it croaked.

 

When you say "random" shifts, there is a lot that goes into that. I'm currently working with a tuning tool to adjust my shift points on my Monte and there is a lot that goes into it. The shift points are dictated by lots of programming in the PCM that uses data like:
- percentage of throttle
- RPM range
- Speed range
and I believe a couple other pieces of data. So in theory, if all the conditions the PCM uses to determine when to shift into different gears are not the same, it will seem "random".

The issue I would be concerned most with is if the trans appears to be "slipping" (when you know it should have shifted and doesn't OR it shifts out of one gear and appears delayed shifting into the next gear). If it appears to be slipping, first thing I would do, validate you have the appropriate amount of fluid in the car (if not that could be an easy fix, but you may need to investigate if you have a fluid leak).

I don't know how robust the scan tools used at your work are, but you could try going for a drive, bring the car to your work, DO NOT turn off the engine, plug the tool in and see if it will report any diagnostics failed during that current ignition cycle (I know the snap-on scan tool I typically use can do that). Or if it can show any historical codes. I suggest this as the computer can throw a code but not illuminate the CEL. Some codes require the condition to occur twice or more consecutively before popping on the CEL. So if you can catch that data with the right scan tool, it may alert you to a pending issue (assuming you are having a situation causing an entry to be stored in the PCM).

 

Great Info Jason!

It sure is nice to have someone like you on the forum that knows his stuff!!!
I will definitely keep that in mind if and when I ever have any trans issues in the furture!

Thanks!

 

the scan tool we have at work does do alot, but its the cut back version than the actual one you buy on the shelf. Its more of a long shift at random times. Once so far its surprised me and lurched a little into 3rd gear & that was what worried me. First time its done it.

It didn't do anything last night on a longer ride home. Drove fine. It just aggravates me that its not something that happens all the time, at random moments.

Oh yea, fluid level is fine.