engine GMC JIMMY 2001 Repair Manual

4-58
Operating the vehicle in tow/haul when lightly loaded or with
no trailer at all will not cause damage. However, there is
no benefit to the selection of tow/haul when the vehicle is
unloaded. Such a selection when unloaded may result in
unpleasant engine and transmission driving characteristics
and reduced fuel economy. Tow/haul is recommended only
when pulling a heavy trailer or a large or heavy load.
Weight of the Trailer
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. And, it can also depend on any
special equipment that you have on your vehicle.Use one of the following charts to determine how much
your vehicle can weigh, based upon your vehicle model
and options.
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.
The Gross Combination Weight Rating (GCWR) is the
total allowable weight of the completely loaded vehicle
and trailer including any passengers, cargo, equipment
and conversions. The GCWR for your vehicle should
not be exceeded.

4-59
C-1500 (2WD)*
Engine Axle Ratio Max. Trailer Wt. GCWR
4800 V8 3.42 5,800 lbs. (2 633 kg) 11,000 lbs. (4 994 kg)
3.73 6,800 lbs. (3 087 kg) 12,000 lbs. (5 448 kg)
5300 V8 3.42 6,800 lbs. (3 087 kg) 12,000 lbs. (5 448 kg)
3.73 7,800 lbs. (3 541 kg) 13,000 lbs. (5 902 kg)
5300 V8 (Suburban/Yukon XL) 3.73 7,700 lbs. (3 495 kg) 13,000 lbs. (5 902 kg)
4.10 8,700 lbs. (3 949 kg) 14,000 lbs. (6 356 kg)
* Weight
-distributing hitch tongue weight 10 percent to 15 percent of trailer weight 1,000 lbs. (454 kg) maximum.

4-60
K-1500 (4WD)*
Engine Axle Ratio Max. Trailer Wt. GCWR
4800 V8 3.73 6,600 lbs. (2 996 kg) 12,000 lbs. (5 448 kg)
4.10 7,600 lbs. (3 450 kg) 13,000 lbs. (5 902 kg)
5300 V8 3.73 7,600 lbs. (3 450 kg) 13,000 lbs. (5 902 kg)
4.10 8,200 lbs. (3 722 kg) 14,000 lbs. (6 356 kg)
5300 V8 (Suburban/Yukon XL) 3.73 7,500 lbs. (3 405 kg) 13,000 lbs. (5 902 kg)
4.10 8,500 lbs. (3 859 kg) 14,000 lbs. (6 356 kg)
5300 V8 (BPH package) 3.73 7,300 lbs. (3 314 kg) 13 000 lbs. (5 902 kg)
4.10 8,200 lbs. (3 722 kg) 14,000 lbs. (6 356 kg)
5300 V8 (Suburban BPH package) 3.73 7,000 lbs. (3 178 kg) 13 000 lbs. (5 902 kg)
4.10 7,800 lbs. (3 722 kg) 14,000 lbs. (3 541 kg)
* Weight
-distributing hitch tongue weight 10 percent to 15 percent of trailer weight 1,200 lbs. (544 kg) maximum.

4-61
C-2500 (2WD)*
Engine Axle Ratio Max. Trailer Wt. GCWR**
6000 V8 (Suburban/Yukon XL)
3.73 8,200 lbs. (3 722 kg) 14,000 lbs. (6 356 kg)
4.10 10,200 lbs. (4 630 kg) 16,000 lbs. (7 264 kg)**
8100 V8 3.73 10,500 lbs. (4 767 kg) 17,000 lbs. (7 718 kg)
(Suburban/Yukon XL)
4.10 12,000 lbs. (5 443 kg) 14,000 lbs. (8 626 kg)
* Weight
-distributing hitch tongue weight 10 percent to 15 percent of trailer weight 1,500 lbs. (681 kg) maximum.
**GCWR limited to 14,000 lbs. (6 356 kg) on vehicles with Z83 suspension.

2500 Suburban/Yukon XL (2WD) equipped with Z83 base suspension limited to 8,200 lbs. (3 722 kg) trailer.
K
-2500 (4WD)*
Engine Axle Ratio Max. Trailer Wt. GCWR
6000 V8 (Suburban/Yukon XL)
3.73 7,900 lbs. (3 586 kg) 14,000 lbs. (6 356 kg)
4.10 9,900 lbs. (4 494 kg) 16,000 lbs. (7 264 kg)**
8100 V8 3.73 10,500 lbs. (4 585 kg) 17,000 lbs. (7 718 kg)
4.10 12,000 lbs. (5 448 kg) 19,000 lbs. (8 626 kg)
* Weight
-distributing hitch tongue weight 10 percent to 15 percent of trailer weight 1,500 lbs. (681 kg) maximum.
**GCWR limited to 14,000 lbs. (6 356 kg) on vehicles with Z83 suspension.

2500 Suburban/Yukon XL (4WD) equipped with Z83 base suspension limited to 7,900 lbs. (3 586 kg) trailer.

4-64 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.
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 inches (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.
Driving with a Trailer
CAUTION:
If you have a rear-most window open and you
pull a trailer with your vehicle, carbon monoxide
(CO) could come into your vehicle. You can't see
or smell CO. It can cause unconsciousness or
death. See ªEngine Exhaustº in the Index. To
maximize your safety when towing a trailer:

Have your exhaust system inspected for
leaks, and make necessary repairs before
starting on your trip.

Keep the rear
-most windows closed.

If exhaust does come into your vehicle
through a window in the rear or another
opening, drive with your front, main
heating or cooling system on and with the
fan on any speed. This will bring fresh,
outside air into your vehicle. Do not use
MAX A/C because it only recirculates the
air inside your vehicle. See ªComfort
Controlsº in the Index.

4-67
You may also want to activate the tow/haul mode if the
transmission shifts too often. See ªTow/Haul Modeº in
the Index.
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 ªEngine Overheatingº
in the Index.Parking on Hills
CAUTION:
You really should not park your vehicle, with a
trailer attached, on a hill. If something goes
wrong, your rig could start to move. People can
be injured, and both your vehicle and the trailer
can be damaged.
But if you ever have to park your rig on a hill, here's
how to do it:
1. Apply your regular brake, 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).

4-68
5. If you have a four-wheel-drive vehicle, be sure the
transfer case is in a drive gear and not in NEUTRAL.
6. Release the regular brakes.
CAUTION:
It can be dangerous to get out of your vehicle if
the shift lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can roll.
If you have left the engine running, the vehicle
can move suddenly. You or others could be
injured. To be sure your vehicle won't move, even
when you're on fairly level ground, use the steps
that follow.
Always put the shift lever fully in PARK (P) with
the parking brake firmly set.
If the transfer case on four-wheel drive vehicles
is in NEUTRAL, your vehicle will be free to roll,
even if your shift lever is in PARK (P). So, be
sure the transfer case is in a drive gear
-- not
in NEUTRAL.
When You Are Ready to Leave After
Parking on a Hill
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.

4-69 Maintenance When Trailer Towing
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, belt, 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.
Trailer Wiring Harness
Your vehicle is equipped with the following wiring
harnesses for towing a trailer.Basic Trailer Wiring Package
The trailer wiring harness, with a seven-pin connector,
is located at the rear of the vehicle and is tied to the
vehicle's frame. The harness connector can be plugged
into a seven
-pin universal heavy-duty trailer connector
available through your dealer.

5-4
2. Get the vehicles close enough so the jumper cables
can reach, but be sure the vehicles aren't touching
each other. If they are, it could cause a ground
connection you don't want. You wouldn't be able
to start your vehicle, and the bad grounding could
damage the electrical systems.
To avoid the possibility of the vehicles rolling, set
the parking brake firmly on both vehicles involved in
the jump start procedure. Put the automatic
transmission in PARK (P), or a manual transmission
in NEUTRAL (N) before setting the parking brake.
If you have a four
-wheel-drive vehicle, be sure the
transfer case is in a drive gear not in NEUTRAL.
NOTICE:
If you leave your radio on, it could be badly
damaged. The repairs wouldn't be covered by
your warranty.
3. Turn off the ignition on both vehicles. Unplug
unnecessary accessories plugged into the cigarette
lighter or in the accessory power outlets. Turn off the
radio and all the lamps that aren't needed. This will
avoid sparks and help save both batteries. And it
could save your radio!
4. Open the hoods and locate the positive (+) and
negative (
-) terminal locations of the other vehicle.
Your vehicle has a remote positive (+) jump starting
terminal and a remote negative (
-) jump starting
terminal. You should always use these remote
terminals instead of the terminals on the battery.
The remote positive (+) terminal is located behind
a red plastic cover near the engine accessory drive
bracket. To uncover the remote positive (+) terminal,
open the red plastic cover.
The remote negative (
-) terminal is located on
the engine drive bracket on all V8 diesel engines.
On V8 engines it is marked ªGND.º
On V6 engines the remote negative (
-) terminal is
located on a tab attached to the engine accessory
drive bracket where it is marked ªGND.º
See ªEngine Compartment Overviewº in the Index
for more information on location.

5-5
CAUTION:
Using a match near a battery can cause battery
gas to explode. People have been hurt doing this,
and some have been blinded. Use a flashlight if
you need more light.
Be sure the batteries have enough water. You
don't need to add water to the ACDelco
battery
(or batteries) installed in every new GM vehicle.
But if a battery has filler caps, be sure the right
amount of fluid is there. If it is low, add water to
take care of that first. If you don't, explosive gas
could be present.
Battery fluid contains acid that can burn you.
Don't get it on you. If you accidentally get it in
your eyes or on your skin, flush the place with
water and get medical help immediately.
CAUTION:
Fans or other moving engine parts can injure you
badly. Keep your hands away from moving parts
once the engine is running.
5. Check that the jumper cables don't have loose or
missing insulation. If they do, you could get a shock.
The vehicles could be damaged too.
Before you connect the cables, here are some basic
things you should know. Positive (+) will go to
positive (+) or a remote positive (+) terminal if the
vehicle has one. Negative (
-) will go to a heavy,
unpainted metal engine part or a remote negative (
-)
terminal if the vehicle has one.
Don't connect positive (+) to negative (
-) or you'll
get a short that would damage the battery and maybe
other parts too. And don't connect the negative (
-)
cable to the negative (
-) terminal on the dead battery
because this can cause sparks.