While merging into highway traffic the truck surged with RPM going to 5,000. Shortly after this event there was a grinding or rattling noise in the transmission bell housing along with unusual shifting behavior and a repeatble vibration + rotational noise between 50 and 60 MPH. The vehicle was brought to the dealer for inspection at least 4 times with claims they could not hear the obvious noise that did not go away. On the last drop off, I picked up the vehicle and the noise was gone but the shifting behavior and the constant vibration from the transmission still persists. The dealer said GMC would replace the transmission for approximately $10,000 but I would need to cover 50% of the cost. Vehicle had 35,700 miles on it and was 4 months beyond the 5yr warranty. Still unrepaired. No warning lamps, messages, or codes. Transmission component failure is imminent based on the vehicle behavior
NHTSA ODI 11669560