I have a 04 Scab 4x4 automatic and I was backing into my driveway tonight and it made a thump and started rolling forward. The truck wont do anything in reverse, but the forward gears all work great.. Is there anything that you guys can think of that would cause this to happen, anything besides a bad trany???? I just had the rearend replaced just over 2 weeks ago, I am about to get sick of this sh*%Y^t. I dont know what to do... HELP