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Note: Chrysler has an entire
section of towing in the Chrysler Academy that salespersons can read. It's
all good info, well laid out and directly from the manufacturer.
Axle ratio. This is the ratio
between the speed of the driveshaft and the speed of the axle shaft (both
are measured in revolutions [turns] per minute). It is important because
the engine needs to run fast enough to make the power it needs without
“lugging” and overheating; running engines faster than needed, though,
wastes fuel, adds wear, and increases noise. The “best” axle ratio
depends on the vehicle, engine, and application, and keeps the engine in
its power band (usually, between peak torque and peak horsepower).
At a low axle ratio, the axle will go faster, given the same engine
speed, than with a high axle ratio. So low axle ratios are called
“fast” because the vehicle goes faster at the same engine speed. Low
ratios, therefore, reduce the speed the engine needs to go (in rpm) at a
particular road-speed (in mph), cutting noise and increasing highway gas
mileage, but also cutting power output. (Old-timers may remember the
"economy ratios" of the mid-1970s, which helped cars like the
Feather Duster get good mileage even with the old slant six engines, but
made acceleration somewhat sluggish compared to their predecessors).
By the same token, a higher ratio (say, 3.9:1 vs 3.2:1) is called
“slow,” and increases power output at the expense of noise and highway
gas mileage, all else being equal.
The transmission itself has the
same internal gearing regardless of axle ratio — but the final drive
ratio will differ.
The axle ratio is changed by changing the size
of the ring and pinion gears inside the differential.
Owners and customers must know the maximum
trailer weight and frontal area (these are normally provided by the trailer
maker, and are often inscribed on a metal plate as well). Each Chrysler,
Dodge, and Jeep car and truck has its own maximum ratings issued by
Chrysler; maximum weight ratings are usually posted on the end of the
driver’s door (while held open), but frontal area usually is not, so this
should be checked at a dealer or with Chrysler's customer service people.
With trucks, there are numerous options that can dramatically change
The total loaded weight of the trailer is also needed, and
this must be supplied by the customer, without guesswork; underestimation
can cause serious problems. The safest method is to use the GTWR, in case
the trailer is ever fully loaded in the future.
weight (TW), the weight of the trailer on the hitch ball, is usually
between 10% and 15% of the trailer load, depending on trailer design and
loading. Putting too much weight onto the ball can seriously damage the
car, but putting too little on can cause the rear end of the truck or car
to lift, cutting traction, increasing trailer sway, or even causing
jackknifing, so the trailer load weight must be distributed properly.
Chrysler recommends putting 60% of the cargo weight in the front half of
the trailer, to put around 10% of the weight on the hitch. Side to side,
weight should be equally distributed.
trailer-and-truck weight rating must also be known; the gross combination
weight (GCW) is the combination of GTW (gross trailer weight) and GVW
(loaded gross vehicle weight). All vehicles have a gross combination weight
rating, or GCWR, which is needed to know the towing limit. Just satisfying
the GCWR is not enough — the other restrictions also apply. As one may
expect, adding weight reduces acceleration and increases stopping
Trailers increase wind and rolling
resistance, so trucks that tow, particularly with trailers over 2,000
pounds or with large frontal areas, may need more power. In
The trailer-tongue load weight has to be factored in
as part of the tow car or truck’s capacity when loading the car or truck.
All trailers, regardless of size, must have their own brake lamps and turn
Though this should be obvious, Chrysler warns: “Never
connect trailer brakes to the vehicle’s hydraulic brake
Finding the right hitch
requires knowing the tongue weight (TW) and loaded trailer weight (GTW) o
the trailer. Accessories may be needed, including transmission coolers,
balls and ball mounts, drawbars, wiring, safety chains, locks, trailer
brake controls, covers, tow bars, and sway controls. The choice of a hitch
and tow vehicle depends on trailer weight classifications.
Up to 2,000 lb, e.g. tent-trailers and small vehicle
trailers. Some cars and minivans can tow these. They can use a
load-carrying (non-equalizing) hitch
Up to 3,500 lb trailers, including single-axle trailers
up to 18 feet long. Chrysler SUVs and Ram trucks can tow these with the
trailer tow group and non-weight-distributing hitch..
Dual axle or large single-axle trailers up to 6,000
pounds can be towed by properly equipped Ram trucks and some Chrysler SUVs,
with a non weight distributing hitch (unless required for a particular
truck); but a weight distributing hitch is recommended.
This class includes the largest recreational
trailers, and requires a weight distributing fifth-wheel or gooseneck
hitch; only specific, properly equipped Rams can tow this.
Class V hitches are large, heavy-gauge-steel hitches designed for
large trucks with high tow ratings, to allow towing without having to use a
weight-distributing hitch. These are sometimes called deadweight or pintle
hitches and require a specially equipped Ram.
The nature of
weight-carrying hitches is obvious from the title; these are the most
popular designs. There are two basic styles:
The parts of a
removable drawbar hitch are:
Regardless of the type,
weight-carrying hitches us a simple ball-and-socket mechanism, not unlike
human knees, to allow trailers to turn around corners. The ball stays with
the truck, and the socket, which fits over the ball, stays with the
trailer. The ball must be sized exactly to the coupler; if too small, it
can bounce loose, and if too large, the trailer won't fit on. A 2 inch
diameter ball is considered medium duty.
On removable drawbar
hitches, the ball attachment must fit the shank hole size and thickness of
the drawbar or shank on the truck. Shanks are usually between 3/4” and 1
3/8”, with lengths from 1 1/2 inch to 2 1/8 inch.
material and shank diameter determine the tow rating of the
1" ball may be rated at 2,000 lb trailer
2" ball may be rated from 3,500 lb to 9,000 lb
2-5/8" ball may be rated from 6,000 lb to
30,000 lb trailer weight
Weight-distributing (or load-equalizing) hitches use leverage
to distribute the tongue weight of the trailer to all the wheels of the
truck and trailer. Air springs, air shocks, and overload springs do not
fulfill this function.
Weight-distributing systems use a receiver on
the truck, a removable hitch head and spring bar assembly, and hookup
brackets to connect the spring bars to the trailer frame. The ball mount is
adjustable for angle and height. The shank of the hitch ball mount fits
into an opening in the hitch platform (two inches square is the most common
size) and is held in place with a pin. The system uses spring bars, also
called equalizing bars, to distribute weight to other areas; these are
usually made of spring steel. Chains at the trailer end attach to snap-up
brackets on the trailer tongue.
The length of the chains varies.
Shorter chains increase tension in the spring bars, so more tongue weight
is transferred to the hitch; each bar then acts as a spring to maintain a
constant pressure on the hitch.
Spring bars have different tensions
built into them, designed to match the trailer weight.
control is adjustable, and applies lateral damping to the trailer tongue to
reduce trailer sway.
fifth-wheel hitch is similar to 18-wheeler type hitches, while a gooseneck
trailer hitch uses a ball in the pickup bed. Both require pickups, and in
both cases the hitches have to be attached to the frame, not the
Fifth-wheel trailer hitch assemblies are most popular with
large trailers, because they reduce trailer sway and make long trailers
easier to manage; gooseneck trailers use a pivoted coupling arm, which fits
onto a ball in the pickup. In both cases, the pickup mounts are over the
non-commercial trailer towing, if the buyer does not exceed the maximum
trailer load or frontal area rating.
With four speed automatics, if
there is frequent shifting while in Drive, the company warns that drivers
must select the “3” range to lock out overdrive (in AutoStick
cars and trucks, drivers must manually shift, but not go into top gear,
including fifth gear on five-speed transmissions). Doing this should
increase performance and increase the life of the
Chrysler warns owners to check the automatic
transmission fluid before towing anything, and to change the fluid and
filter if there is discoloration or a burnt odor. The transmission fluid,
filter, and all driveline lubrication fluids should be changed if the
vehicle regularly tows a trailer for more than 45 minutes of
suggests having a checklist for each tow, which should include checking the
trailer hitch and safety chains, wiring and brake electrical connections,
operation of the trailer brake system (before going into traffic), tire
condition and pressure on both vehicles, all fluid levels, hose
connections, belt tightness, mirrors, and all lamps (including signal
They also recommend practicing driving with a trailer
before each trip, in a relatively safe area with little traffic; this
includes turning, stopping, and backing up.
The recommended process
for backing up is holding the steering wheel at the bottom (6:00 position),
and turning the wheel clockwise to go left, counter-clockwise to go right.
New cars and trucks have to be broken in for at least 500 miles
before towing, and the first 500 miles of towing should be at speeds of
under 51 mph.
Tire inflation is extremely
important; too little pressure results in excess heat, increasing wear and
the risk of blowouts. Overinflated tires can wear unevenly and may not
handle as desired.
All but the smallest trailers, with under 1,000
lb, must use trailer brakes. The most common are electric and surge
brakes; electric brakes can be controlled by an electronic unit which
allows adjustments from inside the truck or car. Hydraulic brakes work by
using the push of the trailer against the car or truck. Both types of
trailer brake usually have a fail-safe that puts the brakes on if the
trailer separates from the tow vehicle.
Trailers should not be
parked on a steep hill; on any hill or grade, wheel blocks or chocks should
be firmly wedged under the tires to avoid slippage, and the parking brake
should be used, firmly.
Towing adds considerable stress and wear to trucks and cars,
and all components (particularly brakes) must be checked more often, with
more frequent fluid changes. After towing through mud, sand, or water,
clean the brake drums (if there are brake drums) and rotors, brake pads and
linings, and front axle U-joints and yokes.
The owner's manual has
more information and should be consulted.
Most states, and common
sense, require towing mirrors on both sides. Anyone who has seen The
Long, Long Trailer knows that passengers should never be in the trailer
while it's towed.
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