Before I get under the wife's Envoy I wanted to see if anyone on here had experience with the AWD system in an Envoy or Trailblazer.

My wife's Envoy started to make a thump when in awd, doesn't make a peep in 2wd and this leads me to the front drive system. Its exactly like driving over a fresh seal strip in the highway and changes with speed. Doesn't seem to mater if its going straight or in a turn so wheel bearings are not it. She said it is more prone to doing it if there is a passenger, not sure how that works but that's what she said. Might be because she turns her music down. LOL I will be driving it to work tomorrow so I will have a better feel for what its doing.

I did a brake job on it last summer so its not an issue there, plus that would make a noise if it was in 2wd or awd.

My guesses are CV joint, slip joint or a transfer case issue. The awd light is not blinking and it is in AWD as tested on these slick roads. I will also check fluid levels.

Any other ideas that I might be over looking besides it being a GM?