Two problems related to body have been reported for the 2001 GMC Sierra. The most recently reported issues are listed below.
My 2001 GMC Sierra pu truck after the second year of ownership began to emit howling sounds from the upper right side of the cab's interior. Gradually the noise got worse. Today it is an almost constant howling sound as if wind is coming through the windshield. I will return it to the dealership next week for a recheck. It is my understanding that other, similar GMC and Chevrolet trucks are doing the same thing.
Vehicle would lean to left, and also pulled left while driving. Been to dealership , and had 2 step coil springs/ insulator , and body shims replaced on left side. Brought vehicle 1/8 inch on all four corners. Later vehicle was high left and low rear left.