clunk in reverse

i have a 2002 yukon and 3 months ago, at about 38,000 miles, I started to have a serious problem.
Everytime i put the auto in reverse, i hear a bad, loud clunk noise from the rear end. Gmc has a bulletin that says that the loud metal clanking noise is normal and no certified dealership will touch the yukon.

Anyone have any sugestions on how to fix the problem or know what type of specalist should check the yukon out ?

Hi have u had your universal joint check for wear it may need to be changed could be worn out U joint. have it replaced it should do the trick worked on my denali 01 ............ok

After checking the U-joints if the noise is still there, there was a bulletin on my 99 yukon where the noise was from the rear yoke. To fix, while the drive shaft is out remove yoke from the differential and pack splines with grease. That was the repair procedure and it worked. For a while anyway.