My '06 LBZ was getting a pump rub (well actually it had it before but someone JB welded it without mentioning it) so I dropped it off at a shop with a new transfer case half, seals, and the pump rub kit. As soon as it was done I dropped it off to have audio work so I'm just now getting a chance to drive it. Went to test my 4 wheel drive and 4 wheel high seemed to work great, but 4 wheel low was a nightmare. When I shifted into it and then gave it gas, it moved slightly then a loud CLUNK and then it just kinda rolled on its own power but didn't accelerate as I applied gas. Any ideas on what would cause this?? Thanks for looking!