I have been told by some that because the atlas is a gear drive transfer case vs the chain in the oem case that you may get noise issues from the front driveshaft turning. Pull the front shaft and see if it still does makes the noise. The only real solution is to run a locking hub on the axle so the drive shaft is not turning when in 2wd. My atlas should be in next week and I have been researching this all week. Keep us posted.