GMC 2013 Sierra Denali Owner's Manual page 300

A weight distributing hitch may be useful with some trailers. Use the following guidelines to determine if a weight
distributing hitch should be used.
1500
1500
1500
2500/3500
Up to 7000 lbs
7001 to 9900 lbs
Over 9900 lbs
Up to 18000 lbs
Optional
Required
Required
Optional
Refer to trailer
manufacturer s
recommendation
50%
100%
Refer to trailer
manufacturer s
recommendation