2003 Bravada AWD problem?

[01silverado2500]

2003 Bravada AWD with 19,000 miles

 

When we purchased it new we had the problem with the front end binding while doing low speed turns. Something was replaced on the transfer case and the binding problem was solved.

 

Sometime last year we began to notice a noise during acceleration, it did not happen all the time, but is now happening more often. The noise is hard to describe, sounds like a thump, clunk, thud that begins at about 25-30mph and when the noise is heard the vehicle acts like it hits a bump on the road...it kinda lurches some. Took the vehicle to the dealer, they could not get it to reproduce the noise so they plugged it into the computer and found no codes. The dealer has no clue what can be causing the problem and said it may not be detected until something fails. I can feel the thump in the steering wheel and it kinda sounds like it is coming from the front end. Im sure that other GM AWD vehicles have had some kind of problem similar to this, I just dont feel too comfortable waiting for something to fail before it can be pin pointed.

 

Any ideas, front axle, hubs, transfer case, rear end?

 

I was leery about this AWD before we purchased the vehicle but now I wish it had the regular 4x4 select mode.