The automatic transaxle on my 2004 Impala with 34,000 miles was working fine. I took it through an automated car wash and opted for the underbody flush and rust proofing in addition to the regular wash. Immediately on exiting the car wash the transaxle upshifted each time with a “clunk”, instead of shifting smoothly as it did before. It did this all the way home. I checked the fluid level in the transmission and it appeared to be overfull and full of bubbles. When I checked the fluid level again the next morning, after warming it up the bubbles were gone, the fluid level was where it should be and now the transaxle shifts smoothly again. Anyone have an idea why running a car through a carwash would create bubbles in the transmission fluid?
The transmission being overfull would definately be a reason for bubbling. The harsh shifting has to do with the computer. Its possible during your undercar flush and rust proofing, there could have been a lost connection somewhere, (Maybe a bad ground). Its possible that the computer has set a trouble code. Have the computer scanned and post back with the results. If there is a code, this would give us a clue as to what happened during the undercar cleaning. Most local auto parts stores will scan for free.
transman