Ford 2003 Excursion Owner's Manual page 182

Driving
Adjusting an equalizing hitch so the rear bumper of the vehicle
is higher than it was unloaded will defeat the function of the
load equalizing hitch and may cause unpredictable handling.
Safety chains
Always connect the trailer's safety chains to the frame or hook retainers
of the vehicle hitch. To connect the trailer's safety chains, cross the
chains under the trailer tongue and allow slack for turning corners.
If you use a rental trailer, follow the instructions that the rental agency
gives to you.
Do not attach safety chains to the bumper.
Trailer brakes
Electric brakes and manual, automatic or surge-type trailer brakes are
safe if installed properly and adjusted to the manufacturer's
specifications. The trailer brakes must meet local and Federal
regulations.
Do not connect a trailer's hydraulic brake system directly to your
vehicle's brake system. Your vehicle may not have enough
braking power and your chances of having a collision greatly increase.
The braking system of the tow vehicle is rated for operation at the
GVWR not GCWR.
Trailer lamps
Trailer lamps are required on most towed vehicles. Make sure your
trailer lamps conform to local and Federal regulations. See your dealer or
trailer rental agency for proper instructions and equipment for hooking
up trailer lamps.
Using a step bumper (if equipped)
The rear bumper is equipped with an integral hitch and only requires a
ball with a 25.4 mm (one inch) shank diameter. The bumper has a 2 270
kg (5 000 lb.) trailer weight and 227 kg (500 lb.) tongue weight capacity.
If it is necessary to relocate the trailer hitch ball position, a
frame-mounted trailer hitch must be installed.
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