'95 Pontiac Transport 3800.Automatic transmission makes a high pitched whistle when in gear and a louder whistle (actually sounds more like a bearing squeal) when in neutral or park. Shifts just fine. My mechanic says the sound is internal to the tranny and is common in this vintage GM cars. He said to just drive it and it may go a long time. He had a car with the same problem and drove 80,000 miles before the tranny began to go. Does anyone concur? Any idea what is causing the sound?
It is possible that the front pump may be making the noise. There is a service bulletin ATRATB281 dated 1-1-1995 on pump noise and it describes a new updated front pump replacement. When rebuilding the transmission the front pump should be replaced with the new design.
It is possible that you could get longer service from the transmission while it is making the noise. Service the transmission regularly and as long as there is no metal in the fluid and the fluid is not burned and you can tolerate the noise and it doesn't get any worse then keep driving. When the transmission starts acting up with shift problems or not going into gear then transmission replacement would required.