One problem related to differential unit has been reported for the 2001 GMC Sierra. The most recently reported issues are listed below.
There was a large "booming" noise coming from vehicle everytime consumer drove it. This noise occurred when pulling away from a stopped position. Consumer took vehicle to dealership, and they greased differential. He was told this would correct the problem. Consumer still experienced the problem dealership said that there was nothing more they could do. Please provide any additional information/attachments.