2007 gmc classic 4x4 z71 sierra tranny problem

hey guys.. i had a warranty issue last thursday for a blown speaker and a few other things.. got the truck back friday afternoon..

going our saturday morning, as i was pulling out of the driveway , right when it shifted or was trying to shift into second... "loud bang or bucking" motor revved up... coasting it would not go anywhere.. came back to a stop had to actualy put it in low 1 to make it back home...

called the dealer ... told me to bring it back in..lol.. so off i go... goin 55 i was able to finally get it to go into 2nd gear and then 3rd..... after about 5 miles then into regular drive.. went to pass a car... it tried downshifting.. loud bang or just sounded like it anyways..motor revving the whole bit... basically felt like it went into neutral... but it did make it to the dealer... they were gone.. but i was still able to use the same rental from before...



what might this be? so i will be prepared to make sure it is done right.. i really hate the idea of just the tranny being rebuilt.. the truck only has 18,000 miles.. i am sure they will be calling me back in the morning.. i have read a few other forums with the 4l60's tranny in the 05-07 having this problem.. whats going on?


i bought the truck as a certified used vehicle from a dealer with only 11,000 miles and got a great deal on it.. but looking back.. the truck always had a intermediat shift 1-2 .. to where u could feel it change and then a slight bump about 1-2 seconds later .. and 2-3 third shift was kinda firm when the truck was cold.. and the usual clunking 3-2 downshift while driving slow