[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.