My suburban was making a "clunking" noise at low speed (<15 mph) turns at what sounded like on the front driver side of the vehicle. I had replaced the upper intermediate steering shaft thinking that would solve the issue, but I was wrong. After replacing the upper steering shaft, I was starting to get "Service 4WD" on the display. I normally keep the vehicle in "auto" and when I tired to turn the dial to 2D or 4H or 4L the light wouldn't change.

Any thoughts/ideas would be helpful.

 

-check the sway bar links for the clunk. palm strike the sway bar close to the link...if it clunks its worn. Or push on the vehicle (open the driver window and push up on the top of the door frame and pull down on the bottom) to sway the body and listen for clunks when it rocks
-have the transfer case control module scanned for codes.

 

Full spectrum code scan is step one of all 4 code families to see what the system is reporting. Everything is just a guess without a full scan.

 

All seems fixed. When I raised the suburban up, the wheel would not move, so I replaced the front differential and thought that was my only fix... With no codes to really go off of and talking to some other people, I also replaced the transfer case shift encoder and that fixed all my issues.