We have a 98 Burb, 138K, 4WD. While driving slow andstraight on level surface, heard one loud snap out of left front. Drove home and smelled brake odor so took left front apart, expecting to find something broken. Found nothing. Put back together and drove again. It drives just fine but can hear some dull intermittant noise up front. Took apart again and can't see anything wrong. Looking for advise on how to test to determine problem.

 

Lots to look at in a 4x4 system. I would start by jacking up the front end (both wheels in the air) and secure it on jackstands. Chock it so it won't roll and put the t'case in neutral (if you can, mine is 2wd, my 4x4 is a Jeep). Then start wigling and turning things. You should be able to find the noise this way. That should get you started anyways. Hard to know just where to start on something like that.