Transfer case issues 2002 gmc sierra 1500

[jasehobbs]

truck has push button four wheel drive and seems to work fine except for the fact that in 2WD, the transfer case seems as if it was locked in for 4WD. I put truck on ramp and in 2WD the tires are harder to spin. We then put a buddies truck on the ramp (identical truck) and in 2WD the rear tires spin much easier. any suggestions or answers as two why this is happening would be greatly appreciated.

Thanks.