2002 avalanche 1500 4x4 wont role backwords

[carl80]

I pulled in front of my house and put it in reverse and started backing up. Then it felt like i hit somthing that stopped me from moving backwords. Got out and looked and found nothing. I tried to back up again and it wouldnt move. But i was able to move forward.
The engine didnt rev up like it was out of gear. I put it in neutral and was able to role it forward but not in reverse. I tried it with motor running and off with no luck. It wouldnt move even a little backwords. I tried puttig in in 4wd hi and it went but not 4wd low. I put it back in 2wd and gave it a little more gas and got it to back up to park but it was popping when it was moving.
I went out this morning to look at it and everything seems fine. Moves forward and back with no problem. Goes into 4wd low but it is quite loud. (Don't know if that's common or not) dont really know what it could be or where to start.

[Blue Bowtie]

There are a lot of possibilities. Almost none of them are good news. One thing to try is to raise the vehicle (all four wheels off the ground) and run it through the ranges. If there is noise in a specific range, attempt to locate it while the vehicle is elevated. There is a remote possibility that the rear axle is the issue, but that is remote. More likely that you will eventually discover metal in the transmission oil pan and a shredded rear planetary set in the trans:





There is a slightly lower probability that you would find a damaged reaction sun shell or hub:



This would normally not produce a popping or grinding noise, but only a buzzing as the spline tries to engage. It also would probably result in a loss of second gear drive.

[j cAT]

how long you owned this ,also what are your servicing of the drive train ? how many miles on it and how were you operating the vehicle prior to this failure.

locked up in reverse can be tranny/diff .. remove drive shaft will narrow it down . drop tranny pan also . checking all fluids for condition ..