Chevrolet 2007 Express 2007 Express Owner's Manual page 275

Because your rear axle now weighs 3,100 lbs
(1 406 kg), you can only put 900 lbs (408 kg) on the
rear axle without exceeding RGAWR. The effect of
tongue weight is about 1.5 times the actual weight.
Dividing the 900 lbs (408 kg) by 1.5 leaves you with
being able to handle only 600 lbs (272 kg) of tongue
weight. Since tongue weight is usually at least
10 percent of total loaded trailer weight, you can
expect that the largest trailer your vehicle can
properly handle is 6,000 lbs (2 721 kg).
It is important that you make sure your vehicle
does not exceed any of its ratings — GCWR,
GVWR, RGAWR, Maximum Trailer Rating
or Tongue Weight. The only way to be sure you
are not exceeding any of these ratings is to weigh
your vehicle and trailer.
Total Weight on Your Vehicle's Tires
Be sure your vehicle's tires are inflated to the
upper limit for cold tires. You'll find these numbers
on the Certification label at the rear edge of the
driver's door or see Loading Your Vehicle on
page 259. Then be sure you don't go over
the GVW limit for your vehicle, or the GAWR,
including the weight of the trailer tongue. If you use
a weight distributing hitch, make sure you don't
go over the rear axle limit before you apply
the weight distribution spring bars.
Hitches
It's important to have the correct hitch equipment.
Crosswinds, large trucks going by and rough roads
are a few reasons why you'll need the right hitch.
The rear bumper on your vehicle is not intended
for hitches. Do not attach rental hitches or
other bumper-type hitches to it. Use only a
frame-mounted hitch that does not attach to the
bumper.
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