I was leaving church this morning and as I would drive forward the rear end was poping and banging (86 K5 blazer 12 bolt open carier and 3.73 gears), so I of course stopped immidately. I was in the lane of traffic so I had to pull off. The truck will not move forward, like you are power breaking or someting and then if you give it enough gas it will lunge forward a few feet and make a loud bang. It will still back up however. I had to leave it there and am having it towed to the shop I work at. What can I expect to look for when I take the rear cover off. I am thinking maybe a carrier or pinion bearing went out. I know the rear diff cover leaks, but not much at all and I checked it this summer. this is my daily driver and I need it fixed asap, unfortunately they guy that owns the shop is on vacation all week and it is 7 degrees out right now so laying on the ground doing the work does not sound appealing. Any ideas on what the problem may be would be appreciated.