GMC 2004 Sierra 1500 Pickup Owner's Manual page 385

Weight Distributing Hitches and Weight
Carrying Hitches
A: Body to Ground Distance
B: Front of Vehicle
When using a weight-distributing hitch, the hitch must
be adjusted so the distance (A) remains the same both
before and after coupling the trailer to the tow vehicle.
If you use a step-bumper hitch, the bumper could
be damaged in sharp turns. Make sure there is ample
room when turning to avoid contact between the
trailer and the bumper.
If you will be pulling a trailer that, when loaded, will
weigh more than 5,000 lbs (2 270 kg) be sure to use a
properly mounted weight-distributing hitch and sway
control of the proper size. This equipment is very
important for proper vehicle loading and good handling
when driving. Always use a sway control if the trailer
will weigh more than these limits. You can ask a
hitch dealer about sway controls.
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