4x4 Clunking, please help...

Hello guys, I have a 1998 GMC Jimmy 4x4 and when its engaged into 4hi the front clunks. My brother said it sounds like its the chain inside the transfer case cause he rebuilds transmissions. But I only talked to him on the phone. I took it to a local garage and the guy took it out and drove it and it didn't clunking for him, so he put it up on the rack and listen to everything under the truck when it was in 4hi and found out everything is fine besides the transfer case, it sounds like rough sand paper rubbing together. if anyone had this problem I need to know cause I would really hate to get the transfer case rebuilt and find out its not that, maybe the cv joints or ball joints or even u-joints there on the front driveshaft, please I need HELP!!!!! Michigan is getting snow and I need the 4x4 to work good not clunking while driving. THANKS

Well, if you took it to a shop and they couldnt diagnose a bad transfer case, then its time to get a real mechanic look at it. My 98 blazer did the whole clunk pop thing for about 4 years, and a week ago the transfer case went poof. So my advice would be to take it to someone that can tell you what is actually wrong with it, there is no reasong they cant tell you if you have a bad joint some where. Do you exercise your 4x4 regularly or just once in a great while?

98 so has the 3 button np233 case that is not made to drive on dry streets or the front end binds up and when you turn it clunks or pops as the different wheel speeds load the front drivetrain up and it has to release. The 4 button Autotrac np236 case has a clutch pack in the transfer to resolve this. It could of course be CV joints starting to fail, hubs, or the front axle coupler not fully engaging on that pass side.

Well I took it back to the shop and find it out, it was the transfer case. I got a new one and got the other one out of the truck and ripped it apart and there was tons of metal shaves inside of it. It looked like a bomb went off inside. But hopefully thats all I have to do, its still apart until the morning so I'll just finish it up then. I just got the truck about 8 months and just tried to use the 4 wheel drive when we got about 3 inches of snow. I tried it when I first got the truck before I bought it but didn't hear it at all. But at least the mechanic heard it this time.