GMC Sierra 2008, Owner'S Manual, Page: 377 / 578

There should be at least six inches of clearance between
the top of the pickup box and the bottom of the trailer
shelf that extends over the box.
Make sure the hitch is attached to the tow vehicle
frame rails. Do not use the pickup box for support.
Safety Chains
You should always attach chains between your
vehicle and your trailer. Cross the safety chains under
the tongue of the trailer to help prevent the tongue from
contacting the road if it becomes separated from the
hitch. Instructions about safety chains may be provided
by the hitch manufacturer or by the trailer manufacturer.
If you are towing a trailer up to 5,000 lbs (2 271 kg)
with a factory-installed step bumper, you may attach
the safety chains to the attaching points on the bumper.
If you are towing a trailer up to your vehicle’s trailer
rating limit you may attach the safety chains to
the attaching point on the hitch platform. If you are
towing with an aftermarket hitch follow the trailer or
hitch manufacturer’s recommendation for attaching
safety chains. Always leave just enough slack so
you can turn with your rig. Never allow safety chains
to drag on the ground.
Trailer Brakes
If your trailer weighs more than 2,000 lbs (900 kg)
loaded, then it needs its own brakes – and they must
be adequate. Be sure to read and follow the instructions
for the trailer brakes so you’ll be able to install, adjust
and maintain them properly.
If your vehicle is equipped with StabiliTrak
®
, your trailer
cannot tap into the vehicle’s hydraulic brake system.
Your trailer brake system can tap into the vehicle’s
hydraulic brake system only if:
•
The trailer parts can withstand 3,000 psi
(20 650 kPa) of pressure.
•
The trailer’s brake system will use less than
0.02 cubic inch (0.3 cc) of fluid from your vehicle’s
master cylinder. Otherwise, both braking systems
won’t work well. You could even lose your brakes.
If everything checks out this far, make the brake tap
at the port on the master cylinder that sends the fluid
to the rear brakes. But don’t use copper tubing for this.
If you do, it will bend and finally break off. Use steel
brake tubing.
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