Engine and rear axle ratio, cab size, bed size and whether 2WD or 4WD makes a difference. Some have a 5th wheel towing capacity as low as 13,800 lbs. Others as high as 21,700 lbs. Find yours. Also check the label inside the driver's door to find the payload/maximum load and make sure it's over 4,000 lbs.
Sierra 3500 HD, regular cab, long box, 2WD DRW (6.0 and 4.10:1 axle) 14,100 (14,100)*
Sierra 3500 HD, regular cab, long box, 4WD DRW (6.0 and 4.10:1 axle) 13,800 (13,800)*
Sierra 3500 HD, regular cab, long box, 4WD DRW (6.6 and 3.73:1 axle) 16,000 (21,700)*
Sierra 3500 HD, extended cab, long box, 2WD DRW (6.0 and 4.10:1 axle) 13,600 (13,600)*
Sierra 3500 HD, extended cab, long box, 4WD DRW (6.6 and 3.73:1 axle) 16,500 (21,500)*
Sierra 3500 HD, extended cab, long box, 4WD DRW (6.0 and 3.73:1 axle) 13,400 (13,400)*
Sierra 3500 HD, extended cab, long box, 4WD DRW ((6.6 and 3.73:1 axle) 17,000 (21,300)*
Sierra 3500 HD, crew cab, long box, 2WD DRW (6.0 and 4.10:1 axle) 13,500 (13,500)*
Sierra 3500 HD, crew cab, long box, 2WD DRW (6.6 and 3.73:1 axle) 16,500 (21,500)*
Sierra 3500 HD, crew cab, long box, 4WD DRW (6.0 and 4.10:1 axle) 13,200 (13,200)*
Sierra 3500 HD, crew cab, long box, 4WD DRW ((6.6 and 3.73:1 axle) 17,000 (21,100)*
2010 GMC Tow Ratings