Caution: The driver can lose control when pulling a trailer if the correct equipment is not used or the vehicle is not driven properly. For example, if the trailer is too heavy, the brakes may not work well or even at all. The driver and passengers could be seriously injured. The vehicle may also be damaged; the resulting repairs would not be covered by the vehicle warranty. Pull a trailer only if all the steps in this section have been followed. Ask your dealer/retailer for advice and information about towing a trailer with the vehicle.

Notice: Pulling a trailer improperly can damage the vehicle and result in costly repairs not covered by the vehicle warranty. To pull a trailer correctly, follow the advice in this section and see your dealer/retailer for important information about towing a trailer with the vehicle.

To identify the trailering capacity of your vehicle, you should read the information in "Weight of the Trailer" that appears later in this section.

Trailering is different than just driving your vehicle by itself. Trailering means changes in handling, acceleration, braking, durability and fuel economy. Successful, safe trailering takes correct equipment, and it has to be used properly.

That's the reason for this part. In it are many time-tested, important trailering tips and safety rules. Many of these are important for your safety and that of your passengers. So please read this section carefully before you pull a trailer.

If you do, here are some important points:

Three important considerations have to do with weight:

Tow/Haul Mode

Tow/haul mode is used when using your vehicle to pull a large or heavy load or trailer. Tow/haul is also useful while pulling a load in rolling terrain, in stop-and-go traffic, or when you need improved low-speed control, such as when parking. The purpose of the tow/haul mode is to do the following:

Tow/haul mode is most effective when the vehicle and trailer combined weight is at least 75 percent of the vehicle's Gross Combination Weight Rating (GCWR). See "Weight of the Trailer" later in this section.

Press the button on the instrument panel to the right of the steering wheel to enable the tow/haul mode.

A light on the instrument panel will illuminate to indicate that tow/haul mode has been selected.

Press the button again to turn off tow/haul mode. The indicator light on the instrument panel will turn off. The vehicle will automatically turn off tow/haul mode every time it is started.

Driving with tow/haul mode activated without a heavy load or with no trailer will cause reduced fuel economy and unpleasant engine and transmission driving characteristics, but will not cause damage.

How heavy can a trailer safely be?

It depends on how you plan to use your rig. For example, speed, altitude, road grades, outside temperature and how much your vehicle is used to pull a trailer are all important. It can also depend on any special equipment that you have on your vehicle, and the amount of tongue weight the vehicle can carry. See "Weight of the Trailer Tongue" later in this section for more information.

Maximum trailer weight is calculated assuming only the driver is in the tow vehicle and it has all the required trailering equipment. The weight of additional optional equipment, passengers and cargo in the tow vehicle must be subtracted from the maximum trailer weight.

Use the following chart to determine how much your vehicle can weigh, based upon your vehicle model and options.

You can ask your dealer for our trailering information or advice, or you can write us at our Customer Assistance Offices. See Customer Assistance Offices for more information.

The tongue load (A) of any trailer is an important weight to measure because it affects the total gross weight of your vehicle. The Gross Vehicle Weight (GVW) includes the curb weight of the vehicle, any cargo you may carry in it, and the people who will be riding in the vehicle. If you have a lot of options, equipment, passengers or cargo in your vehicle, it will reduce the tongue weight your vehicle can carry, which will also reduce the trailer weight your vehicle can tow. If you will tow a trailer, you must add the tongue load to the GVW because your vehicle will be carrying that weight, too. See Loading the Vehicle for more information about your vehicle's maximum load capacity.

The trailer tongue weight (A) should be 10 percent to 15 percent of the total loaded trailer weight (B), up to a maximum of 500 lbs (227 kg) with a weight carrying hitch. The trailer tongue weight (A) should be 10 percent to 15 percent of the total loaded trailer weight (B), up to a maximum of 700 lbs (318 kg) with a weight distributing hitch.

Do not exceed the maximum allowable tongue weight for your vehicle. Choose the shortest hitch extension that will position the hitch ball closest to the vehicle. This will help reduce the effect of trailer tongue weight on the rear axle.

Your spare tire carrier is behind the tailgate. If your hitch extension is too short, the spare tire may interfere with trailer coupling or trailer tongue jack operation on some types of trailers.

After you've loaded your trailer, weigh the trailer and then the tongue, separately, to see if the weights are proper. If they aren't, you may be able to get them right simply by moving some items around in the trailer.

Trailering may also be limited by the vehicle's ability to carry tongue weight. Tongue weight cannot cause the vehicle to exceed the GVWR (Gross Vehicle Weight Rating) or the RGAWR (Rear Gross Axle Weight Rating). The effect of additional weight may reduce your trailering capacity more than the total of the additional weight.

Consider the following example:

A vehicle model base weight is 5,500 lbs (2 495 kg); 2,800 lbs (1 270 kg) at the front axle and 2,700 lbs (1 225 kg) at the rear axle. It has a GVWR of 7,200 lbs (3 266 kg), a RGAWR of 4,000 lbs (1 814 kg) and a GCWR (Gross Combination Weight Rating) of 14,000 lbs (6 350 kg). The trailer rating should be:

You can expect tongue weight to be at least 10 percent of trailer weight (850 lbs (386 kg)) and because the weight is applied well behind the rear axle, the effect on the rear axle will be greater than just the weight itself, as much as 1.5 times as much. The weight at the rear axle could be 850 lbs (386 kg) X 1.5 = 1,275 lbs (578 kg). Since the rear axle already weighs 2,700 lbs (1 225 kg), adding 1,275 lbs (578 kg) brings the total to 3,975 lbs (1 803 kg). This is very close to, but within the limit for RGAWR as well. The vehicle is set to trailer up to 8,500 lbs (3 856 kg).

But let's say your specific vehicle is equipped with some of the latest options and you have a front seat passenger and two rear seat passengers with some luggage and gear in the vehicle as well. You may add 300 lbs (136 kg) to the front axle weight and 400 lbs (181 kg) to the rear axle weight. Your vehicle now weighs:

Weight is still below 7,200 lbs (3 266 kg) and you may think that you should subtract 700 additional pounds (318 kg) from your trailering capacity to stay within GCWR limits. Your maximum trailer would only be 7,800 lbs (3 538 kg). You may go further and think you must limit tongue weight to less than 1,000 lbs (454 kg) to avoid exceeding GVWR. But, you must still consider the effect on the rear axle. 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.

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 the Vehicle . 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.

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.

Weight-Distributing Hitches and Weight Carrying Hitches

When using a weight-distributing hitch, the hitch must be adjusted so that the distance (A) remains the same both before and after coupling the trailer to the tow vehicle.

If you will be pulling a trailer that, when loaded, will weigh more than 5,000 lbs (2 268 kg) be sure to use a properly mounted weight-distributing hitch and sway control of the proper size. This equipment is very important for proper vehicle loading and good handling when driving. You should always use a sway control if your trailer will weigh more than these limits. You can ask a hitch dealer about sway controls.

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. Always leave just enough slack so you can turn with your rig. Never allow safety chains to drag on the ground.

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.

Your trailer brake system can tap into the vehicle's hydraulic brake system only if:

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.

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 as responsive as your vehicle is by itself.

Before you start, check all trailer hitch parts and attachments, safety chains, electrical connector, lamps, 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.

During your trip, check occasionally to be sure that the load is secure, and that the lamps and any trailer brakes are still working.

Stay at least twice as far behind the vehicle ahead as you would when driving your vehicle without a trailer. This can help you avoid situations that require heavy braking and sudden turns.

You'll need more passing distance up ahead when you're towing a trailer. Because you're a good deal longer, you'll need to go much farther beyond the passed vehicle before you can return to your lane.

Hold the bottom of the steering wheel with one hand. Then, to move the trailer to the left, just move that hand to the left. To move the trailer to the right, move your hand to the right. Always back up slowly and, if possible, have someone guide you.

Notice: Making very sharp turns while trailering could cause the trailer to come in contact with the vehicle. The vehicle could be damaged. Avoid making very sharp turns while trailering.

When you're turning with a trailer, make wider turns than normal. Do this so your trailer won't strike soft shoulders, curbs, road signs, trees or other objects. Avoid jerky or sudden maneuvers. Signal well in advance.

The arrows on your instrument panel will flash whenever you signal a turn or lane change. Properly hooked up, the trailer lamps will also flash, telling other drivers you're about to turn, change lanes or stop.

When towing a trailer, the arrows on your instrument panel will flash for turns even if the bulbs on the trailer are burned out. Thus, you may think drivers behind you are seeing your signal when they are not. It's important to check occasionally to be sure the trailer bulbs are still working.

Reduce speed and shift to a lower gear before you start down a long or steep downgrade. If you don't shift down, you might have to use your brakes so much that they would get hot and no longer work well.

You can tow in DRIVE (D). You may want to shift the transmission to THIRD (3) or, if necessary, a lower gear selection if the transmission shifts too often (e.g., under heavy loads and/or hilly conditions).

You may also want to activate the tow/haul mode if the transmission shifts too often. See "Tow/Haul Mode" earlier.

When towing at high altitude on steep uphill grades, consider the following: Engine coolant will boil at a lower temperature than at normal altitudes. If you turn your engine off immediately after towing at high altitude on steep uphill grades, your vehicle may show signs similar to engine overheating. To avoid this, let the engine run while parked (preferably on level ground) with the automatic transmission in PARK (P) for a few minutes before turning the engine off. If you do get the overheat warning, see Engine Overheating .

Caution: Parking the vehicle on a hill with the trailer attached can be dangerous. If something goes wrong, the rig could start to move. People can be injured, and both the vehicle and the trailer can be damaged. When possible, always park the rig on a flat surface.

But if you ever have to park your rig on a hill, here's how to do it:

1. Apply your regular brakes, but don't shift into PARK (P) yet.
2. Have someone place chocks under the trailer wheels.
3. When the wheel chocks are in place, release the regular brakes until the chocks absorb the load.
4. Reapply the regular brakes. Then apply your parking brake and shift into PARK (P).
5. Release the regular brakes.

1. Apply your regular brakes and hold the pedal down while you:

•	start your engine,

•	shift into a gear, and

•	release the parking brake.

2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the chocks.

Your vehicle will need service more often when you're pulling a trailer. See the Maintenance Schedule for more on this. Things that are especially important in trailer operation are automatic transmission fluid (don't overfill), engine oil, axle lubricant, belts, cooling system and brake system. Each of these is covered in this manual, and the Index will help you find them quickly. If you're trailering, it's a good idea to review these sections before you start your trip.

Check periodically to see that all hitch nuts and bolts are tight.

Heavy-Duty Trailer Wiring Package

Your vehicle is equipped with a trailer towing harness. This harness with a seven-pin universal heavy-duty trailer connector is attached to a bracket on the hitch platform.

The trailer towing harness contains the following trailer circuits:

A jumper harness for an electric trailer brake controller and a trailer battery feed fuse may be included with this trailering package. See "Instrument Panel Jumper Wiring Harness" later in this section.

If you need to tow a light-duty trailer with a standard four-way, round pin connector, an adapter may be included. See "Four-Wire Harness Adapter" later in this section.

Instrument Panel Jumper Wiring Harness

Notice: If your vehicle has factory or dealer-installed HUMMER off-road lamps, the place where an electric trailer brake connection must be made is already in use. Do not attempt to double-up or "piggyback" the connection, because this could cause a failure or damage to your vehicle, the electric trailer brake system, or both. If you want to connect a trailer with electric brakes to your vehicle, see your dealer to disconnect the off-road lamps. Also, read Add-On Electrical Equipment for more information.

This harness may be included with your vehicle as part of the heavy-duty trailer wiring package.

Caution: Be sure to use only the correct trailer brake harness, the one intended for use on your vehicle. If you use some other trailer brake harness, even if it seems to fit, your trailer brakes may not work at all. You could have a crash in which you or others could be injured. Use only the trailer brake harness intended for your vehicle. If it is no longer available to you, be sure to get a proper replacement from your dealer.

This harness is for an electric brake controller and includes a trailer battery feed fuse. It should be installed by your dealer or a qualified service center.

Connect the adapter with the tab pointing up. The flip cap on the vehicle's seven-wire harness will lock onto the tab (see arrow in the previous graphic) and help hold the adapter in place. Plug the four-way round pin connector onto the adapter.