1999 Grand Prix GT transmission problem?

[Zulli85]

Hi there guys. Lately I have been experiencing a problem that has been coming and going with my car. On occasion my Grand Prix will start to shift very hard which shakes the entire car. The engine will also make a kind of whining noise when the accelerator is depressed. This problem has been coming and going for a few weeks now, and from what I can tell it only happens when the car has been running for at least 20 or so minutes.

This happened for about the 3rd or 4th time two nights ago, but this time I noticed a pretty huge puddle beneath the car after it was sitting in my garage for a couple of hours. This made me think that transmission fluid is low, which it probably is, but do you think there is a leak somewhere? Maybe a hose?

Any input, advice and/or useful information will be highly appreciated. Just wanted to check here first before I take it to the garage. Thanks!

[2000gpgtx]

Sounds like a PCS failure (common to 4T65E trans). I hope the puddle you're seeing isn't the extension housing shatter associated with the differential break that sometimes results from the full line pressure command hard shift. Have a diagnostic scan performed and check for P07XX codes as these codes will not necessarily light the MIL. If the puddle is closer to the right side of the car, it's more than likely destroyed the differential and broken the extension housing. PCS replacement requires the case be split (located on valve body in end pan, rather than accessed from the bottom), which will require the cradle be dropped for clearance. The 'whining' noise is also associated with the PCS failure as the PCM will command full line pressure, taxing the transmissions oil pump which in turn will make such a 'whine' under load.

[tblake]

Common issue on the 4t65e transmissions.

See the link below....

http://www.automotiveforums.com/vbul...d.php?t=920671