1997 GMC Jimmy Owner's Manual - Page 214

Will you have to make any holes in the body of your vehicle when you install ti trailer hitch'? If you do. then be sure to seal the holes later when you remove the hitch. If you d o n ' t seal them, deadly carbon monoxide (CO) f~-om your exhaust can get into your vehicle (see "Carbon Monoxide" i n the Index). Dirt and water can, too. Trailer Brakes If your trailer weighs more than 1.000 Ibs. (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 n1aintain them properly. Safety Chains you should always attach chains between yo11rvehicle and your trailer. Cross the safety chains under the tongue of the trailer s o that the tongue w i l l not drop to the road if it becomes separated from the hitch. Instructions about safety chains may be provided by the hitch manufilcturer or by the trailer manufacturer. Follow the manufacturer's recommendation for attaching safety chains and clo not attach them to the blmper. Always leavejust enough slack so you can turn with your rig. And, never a l l o w safety chains to drag on the ground. Your trailer*sbrake system can tap into the vehicle's hydraulic brake system only if: The trailer parts can withstand 3.000 psi (20 650 kPa) o f pressure. 0 The traileras brake system will use less th;m 0.02 cubic inch (0.3 cc) o f fluid from your vehicle's master cylinder-. Otherwise. both braking systems won't work well. You could even lose your brakes. I f everything checks out this far, then make the brake tluid tap at the port on the master cylinder that sends fluid to the ear brakes. But don't use copper tubing for this. If you do, it will bend and finally break off. Use steel brake tubing. 4-49