I have 2007 H2 with 250K miles and have a loud front end clunk at hard acceleration. Only heard from a stop. Occurs in high and low gear. Changed transfer case fluid appears normal. No adverse sound at all while driving. Could the front u-joints cause this? Any suggestions much appreciated. Also had the upper and lower ball joints replaced a while back.

 

have you checked the diff bushings, lower control arm bushings or your motor mounts?