One problem related to driveshaft has been reported for the 2001 GMC Sierra. The most recently reported issues are listed below.
Automatic transmission makes gear noise in 1st and 4th gears. At purchase, vehicle had bad vibration problem. Dealer balanced wheels, which did not eliminate problem. Dealer tested tires and found one defective tire. . . The other three had to be "indexed" on the wheels. Driveshaft, suspension components/hardware and parts of the chassis have significant rust. (tiresize: p235/75r16).