I've had 2 failures, one at 34K and again at 80K. Both times was the Sun Shell busting apart. Both times on a 1-2 shift, one on a freeway on-ramp, second pulling out of a shopping mall. Neither time was I towing. Both times, there was a stall in forward movement then a "slam" shift into 2nd, with resulting no 2,4,R. The first repair was under warranty by dealer. The second repair I had a non-dealer repair shop use the Beast Sun Shell and the 3-4 clutch pack changed to Alto.
I do have a Wester's 91 Hot tune with the majority of TQM removed during both instances.