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.
Knowing axle ratios
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.
Trailer and combined weights
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 ratings.
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.
Trailer tongue 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.
The combined 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 distances.
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 addition:
- Trailers over 1,000 lb should have their own brakes;
- Trailers over 2,000 lb need the truck's best engine cooling and an auxiliary transmission cooler (for automatics), and brakes for all wheels;
- Conventional trailers over 5,000 lb (or with a tongue weight over 500 lb) need a weight-distributing hitch; and
- Trailers over 12,000 lb must be goosenecks or fifth-wheel designs.
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 signals.
Though this should be obvious, Chrysler warns: “Never
connect trailer brakes to the vehicle’s hydraulic brake
Classes of trailers
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.
Class I — Light-Duty
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
Class II — Medium-Duty
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..
Class III — Heavy-Duty
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.
Class IV — Extra-Heavy-Duty
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.
Choosing a hitch
The nature of weight-carrying hitches is obvious from the title; these are the most popular designs. There are two basic styles:
- Fixed Drawbar — The ball platform is welded on
- Removable Drawbar — The ball platform is removable, by taking out a pin.
The parts of a removable drawbar hitch are:
- Hitch receiver or hitch box: The opening that receives the shank of the hitch ball mount
- Shank: Holds the hitch ball mount, locked with a heavy steel pin
- Hitch box cover: Protects the hitch box from rust or incidental damage when the shank is not installed
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.
The ball material and shank diameter determine the tow rating of the ball.
1" ball may be rated at 2,000 lb trailer
2" ball may be rated from 3,500 lb to 9,000 lb trailer weight
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.
The sway control is adjustable, and applies lateral damping to the trailer tongue to reduce trailer sway.
Fifth-Wheel and Gooseneck Hitches:
A 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 bed.
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 rear axle.
Chrysler towing warranties
Chrysler allows 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 transmission.
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 continuous operation
Towing advice from Chrysler
Chrysler 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 flashers).
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.
- Avoid sudden moves
- You need more room on the inside of turns, because the trailer wheels will go in further
- Signal long in advance for a lange change, and leave much more room (for the trailer) behind
- It will take more time and distance to pass or change lanes, and more time and distance to stop
- More downshifting may be needed to accelerate or climb hills; downshifting on hills adds driveline friction to hold back the car or truck, reducing the load on the brakes.
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.