One problem related to clunking noise has been reported for the 1999 GMC Sierra. The most recently reported issues are listed below.
1. ) anti lock brake system seems to activate and not allow vehicle to stop nearly as quick as if there was no anti lock system. This has occurred 5 to ten times, but has not resulted in a wreck. 2. ) clunking noise in rear end area - sounds line excessive backlash in rear end.