Rumbling and possibly shifting problem in the 30-60 mph range…Transmission does not seem to be slipping but it seems like it is trying to find a gear at possibly the wrong RPM
Ask you shop to verify the speedometer and transmission input-shaft-rpm sensors are working correctly. Are there any warning lights lit up on the dashboard? I’m presuming the transmission fluid is in good shape and at the correct level.
Chevy has had problems with a transmission shudder in multiple year vehicles. some have been taken care of with having the trans fluid and filter changed.
others were fixed by software updates. some were more involved. here are a couple of other technical service bulletins I have found.
Knowing the engine and if RWD or 4x4 and mileage would help a little…
And if any codes…
+1 for above…
Definitely lots of issues with the transmissions, might want to contact the dealer to see what they say… Or take it to a reputable transmission shop with updated scanner(s) tools and software, those 8+ speed automatics are not your fathers transmission anymore…
You would not want your primary family Dr doing heart surgery, no more than you want a regular shop, that is not up to date and trained, on these late model trans trying to diag them and or repair them…
They have had some valve body wear issues as well… Even a little wear in the pulse
damper (accumulator) bores has an effect on solenoid pressure to the controlling clutch
regulator valves. Flare, harsh and erratic shifts all are a result of poor clutch
control. A worn damper bore must be corrected to provide a smooth solenoid
signal to the clutch regulator it serves. The smoother the solenoid signal, the
more consistent and cleaner the shifts and TCC will be. Also some breakage in the PR valve/shuttle valve bore area, as well as a few other things…
A qualified shop can repair the valve body or replace it were a lot of shops would just want to replace the whole trans…
But get it properly checked out by a pro…
Thank you, George…I will definitely have that checked…This is a 4WD 3.6 litre V6 with 50k miles…Trans fluid level is OK and looks good…I am the second owner so I don’t believe the fluid has been changed…I did see in a bulletin that a relearn process might affect this problem, so I will try that…It does not seem to be slipping at any RPM, but it seems to be searching for a gear…Thanks again
Thanks for the information and details in the bulletins…Seems to be a fairly common problem…These transmissions are a lot more complicated than I imagined…The vehicle has only 50k miles, so I am disappointed that tranny problems should occur so soon…One of the bulletins mentioned doing a relearn procedure…might change the symptoms…but problem may come back again…So I will get it checked by somebody specialized in these problems…Thanks again…