Towing a Recreation Vehicle (RV) is a common practice, but did you ever consider what towing does to the tow vehicle’s powertrain?
Let’s start by explaining what a vehicle powertrain is. The powertrain on a rear wheel drive vehicle includes every component required to get the power from the engine to the rear axle and the vehicle’s wheels. The vehicle’s engine is rated in horse power and torque. To get that torque to the vehicle’s rear wheels, it must first go through several components in the vehicle’s drive train.
First, the power leaving the engine goes to the transmission. In this case it’s an automatic transmission. The transmission provides you with a variety of gear ranges based on the speed and torque for the driving conditions.
Most modern-day vehicle’s used for towing or hauling heavy loads have a tow/haul mode. If you are towing and the transmission keeps shifting in and out of gears you can use the tow/haul. Read your owner’s manual for more information on Tow/haul and gear selection when towing.
From the transmission the power is delivered to the rear axle by way of the driveshaft. The axle uses a pinion and ring gear to get the power to both rear wheels. Axles come with different gear sets, which is typically referred to as the axle ratio.
The axle ratio is a comparison of how many times the drive shaft rotates in relationship to how many times the rear wheels rotate.
Axle rations are expressed in numeric values. For example, a 3.73 to 1 ratio means the drive shaft, or pinion gear rotates 3.73 times for each rotation of the wheels, or the ring gear.
The lower the numeric value is the better the axle is for fuel economy, and the higher the numeric value the better the axle is for towing.
Under normal driving conditions all of these components do their individual jobs with very little stress, and with operating temperatures in the normal ranges. When you add additional weight to the vehicle, like a travel trailer or 5th wheel trailer, the components we just discussed are expected to do the same job as before, with the added weight and stress on the components.
Let’s see what happens under this scenario
With additional weight comes more heat and friction as the driveline does its job. When the coolant, oil and fluids run hotter than normal its more difficult to lubricate the metal on metal components, causing increased friction and wear.
Transmission Oil Cooler
This is why truck manufacturers offer tow packages. To counter the effects of the added stress, and optimize towing, tow packages offer things like a heavy-duty cooling system, engine oil coolers and transmission coolers.
Many go even further and provide an upgraded suspension system, larger brakes, a built-in trailer brake controller and tow mirrors.
And when you use the proper hitch components, like a weight distributing hitch, it helps lessens the stress on the power train when you are towing a trailer. You can see how a tow package is designed to help deal with the added heat and stress placed on the vehicle’s power train.
But, possibly the most important thing we as owners can do is make sure the engine coolant, oil, fluids and all filters are replaced on a regular schedule.
Fresh oil, fluids and filters provide the highest degree of lubrication qualities, and are the best defense against heat, friction and stress on power train components.
Mark J. Polk
RV Education 101