The Sun Gear failed on my 98 GMC pickup at 59k miles and while 350 miles from home. The transmission shop immediately told me my problem when I described the loss of reverse, 2nd and 4th gears. The technician also showed me what he expected to find during the tear down.
He did this because he had 2 more transmissions with the same problem on his workbench. He said this was a common problem he frequently encountered with the 1997-1999 GM transmission.
After it was repaired, they showed me a 2000 ATRA Manual which said "the sun gear shell was faulty due to its manufacturing process". and to check the part number of the replacement to be sure the new part was received due to some of the old part being in the GM supply chain.
I feel if GM has used a faulty part, they should step up to the plate and make matters right, which to this point they have stonewalled me. I'm trying at this point to get the ball rolling by taking this issue public. Any help out there?