GMC 1994 Yukon Owner's Manual page 200

Trailer Brakes
lr
your trailer weighs more than 1,000 pounds (450 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.
Your trailer brake system can tap into your vehicle's hydraulic brake system,
but consider the following:
0
Will the trailer brake system use more than 0.02 cubic inch (0.3 cc) of
fluid from your vehicle's master cylinder? If it will, don't tap into your
vehicle's brake system. Both braking systems won't work well, and you
could even lose your brakes altogether.
0
Will the trailer brake parts take 3,000 psi (20 650 kPa) of pressure? If
not, the trailer brake system must not be used with your vehicle.
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.
Driving with a Trailer
Towing a trailer requires a certain amount of experience. Before setting out
for the open road, you'll want to get to know your rig. Acquaint yourself
with the feel of handling and braking with the added weight of the trailer.
And always keep in mind that the vehicle you are driving is now a good
deal longer and not nearly so responsive as your vehicle is by itself.
Before you start, check the trailer hitch and platform, safety chains,
electrical connector, lights, tires and mirror adjustment. If the trailer has
electric brakes, start your vehicle and trailer moving and then apply the
trailer brake controller by hand to be sure the brakes are working. This lets
you check your electrical connection at the same time.
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