Mercedes-Benz ML320. Service manual - part 95

207

Operation

Driving instructions

Trailer hitches

앫

Only install a trailer hitch receiver ap-
proved for your vehicle.

For information on availability and in-
stallation, see your authorized 
Mercedes-Benz Light Truck Center.

앫

The bumpers on your vehicle are not 
designed for use with clamp-type hitch-
es.

Do not attach rental hitches or other 
bumper-type hitches to them.

앫

To reduce the possibility of damage, re-
move the hitch ball adaptor from the 
receiver when not in use.

Electrical connections

The vehicle is prewired to accept the sev-
en-wire harness included in the 
Mercedes-Benz approved trailer hitch re-
ceiver kit. 

An additional four-pole conversion plug is 
included in the Mercedes-Benz supplied 
trailer hitch receiver kit. 

For further information, see your autho-
rized Mercedes-Benz Light Truck Center.

Vehicle and trailer weights and ratings

Gross Vehicle Weight Rating (GVWR) is the 
maximum permissible vehicle weight:
6614 lbs (3000 kg).

Gross Vehicle Weight (GVW):
Comprises weight of vehicle including fuel, 
tools, spare wheel, installed accessories, 
passengers, cargo and trailer tongue. It 
must never exceed the GVWR.

Gross Axle Weight Rating (GAWR) is the 
maximum permissible axle weight:

Gross Trailer Weight (GTW) is the maxi-
mum permissible trailer weight to be 
towed:
5000 lbs (2260 kg).

Trailer Tongue Weight Rating (TWR) is the 
maximum permissible weight on the trailer 
tongue:
500 lbs (225 kg) limit for Mercedes-Benz 
approved hitch receiver.

front
rear

2976 lbs
3858 lbs

(1350 kg)
(1750 kg)

208

Operation

Driving instructions

Loading a trailer

앫

When loading a trailer, you should ob-
serve that neither the permissible GTW, 
nor the GVWR are exceeded.

Maximum permissible values are listed 
on the safety compliance certification 
labels for the vehicle and for the trailer 
to be towed.
The lowest value listed must be select-
ed when determining how the vehicle 
and trailer are loaded.

앫

The tongue weight at the hitch ball 
must be added to the GVW to prevent 
exceeding your Mercedes-Benz tow 
vehicle’s rear GAWR.

Checking weights of vehicle and trailer

앫

To assure that the tow vehicle and trail-
er are in compliance with the maximum 
permissible weight limits have the load-
ed rig (tow vehicle including driver, pas-
sengers and cargo, trailer fully loaded) 
weighed on a commercial scale.

앫

Check the vehicle’s front and rear 
Gross Axle Weight (GAW), the GTW and 
TW.

The values as measured must not be 
exceeded, according to the weight list-
ed under “Vehicle and trailer weight 
and ratings”.

Attaching a trailer

Observe maximum permitted trailer 
dimensions (width and length).

Most states and all Canadian provinces 
require

앫

safety chains between your tow vehicle 
and the trailer.

The chains should be crisscrossed un-
der the trailer tongue. They must be at-
tached to the hitch receiver, and not to 
the vehicle’s bumper or axle.

Be sure to leave enough slack in the 
chains to permit turning corners.

앫

a separate brake system at various 
trailer weights.

앫

a break-away switch on trailers with a 
separate brake system.

The switch activates the trailer brakes 
in the possible event that the trailer 
might separate from the tow vehicle.

i

We recommend loading the trailer in 
such a manner that it has a tongue 
weight (TW) between 10% and 15% of 
the GTW.

209

Operation

Driving instructions

Towing a trailer

There are many different laws, including 
speed limit restrictions, having to do with 
trailer towing. Make sure your rig will be le-
gal, not only for where you reside, but also 
for where you will be driving. A good 
source for this information can be the po-
lice or local authorities.

Note the following points, when driving 
with the trailer:

앫

In order to gain skill and an under-
standing of the vehicle’s behavior, you 
should practice turning, stopping and 
backing up in an area which is free from 
traffic.

앫

Before you start driving check the

앫

trailer hitch

앫

break-away switch

앫

safety chains

앫

electrical connections

앫

lighting and tires

Adjust the mirrors to permit unobstructed 
view beyond rear of trailer.

앫

If the trailer has electric brakes, start 
your vehicle and trailer moving slowly, 
and then apply only the trailer brake 
controller by hand to be sure the 
brakes are working properly.

앫

Always secure items in the trailer to 
prevent load shifts while driving.

앫

When towing a trailer, check occasion-
ally to be sure that the load is secure, 
and that lighting and trailer brakes (if 
so equipped) are functioning properly.

앫

Take into consideration that when tow-
ing a trailer, the handling characteris-
tics are different and less stable from 
those when operating the vehicle with-
out a trailer.

It is important to avoid sudden maneu-
vers.

!

Do not connect a trailer brake system 
(if trailer is so equipped) directly to the 
vehicle’s hydraulic brake system, as 
your vehicle is equipped with antilock 
brakes. If you do, neither the vehicle’s 
brakes nor the trailer’s brakes will func-
tion properly.

i

The provided vehicle electrical wiring 
harness for trailer towing has a brake 
signal wire (color orange) for hook-up 
to a brake controller.

You should consider using a trailer 
sway control system. For further infor-
mation see your authorized 
Mercedes-Benz Light Truck Center.

210

Operation

Driving instructions

앫

The vehicle and trailer combination is 
heavier, and therefore is limited in ac-
celeration and climbing ability, and re-
quires longer stopping distances.

It is more prone to reacting to side wind 
gusts, and requires more sensitive 
steering input.

앫

If possible, do not brake abruptly, but 
rather engage the brake slightly at first 
to permit the trailer to activate its 
brake. Then increase the braking force.

앫

If the transmission hunts between 
gears on inclines, manually shift to a 
lower gear (select 4, 3, 2 or 1).

A lower gear and reduction of speed re-
duces the chance of engine overload-
ing and/or overheating.

앫

On very steep inclines, not manageable 
with gear selector lever in position 1, 
switch transfer case to LOW RANGE 
mode (

컄

page 125).

앫

When going down a long hill, shift into 
a lower gear and use the engine’s brak-
ing effect.

Avoid riding the brakes, thus overheat-
ing the vehicle and trailer brakes.

앫

If the engine coolant rises to an ex-
tremely high temperature (coolant tem-
perature needle approaching the red 
zone) when the air conditioning is on, 
turn off the air conditioning system.

Engine coolant heat can be additionally 
vented by opening the windows, 
switching the climate control fan speed 
to high and setting the temperature 
control to the maximum hot position.

앫

Extreme care must be exercised since 
your vehicle with a trailer will require 
additional passing distance ahead than 
when driving without a trailer.

Because your vehicle and trailer is 
longer than your vehicle alone, you will 
also need to go much farther ahead of 
the passed vehicle before you can re-
turn to your lane.

!

If the trailer should begin to sway, re-
duce the vehicle’s speed and use the 
brake controller by hand to straighten 
out the vehicle and trailer.

In no case should you attempt to 
straighten out the tow vehicle and trail-
er by increasing the speed or overstee-
ring and stepping on the brakes.