Late summer is when a lot of us finally head up to Wisconsin with the boat or the camper in tow. It's also when I hear about overheated transmissions. Towing in August heat is about the hardest work most trucks and SUVs ever do.
Why heat is the enemy
When you tow, your engine works harder and runs hotter, and so does your transmission. Your transmission fluid does several jobs at once: it lubricates the gears, cools the transmission and carries the hydraulic pressure that makes it shift. When it runs hot for long stretches, it oxidizes and breaks down faster. Varnish builds up, shifts get sloppy, and parts wear.
Engine oil goes through the same thing. Add a long grade, a headwind and a 90-degree afternoon, and the oil is working at the top of its range for hours.
Check your owner's manual for "severe service"
Most owner's manuals list towing as severe service and recommend more frequent oil and fluid changes when you tow. Plenty of people never read that page, so look it up for your truck. If you tow regularly, the severe-service schedule is the one that applies to you.
Before you hook up
- Engine oil. Is it due, or close? If so, change it before the trip rather than after. A synthetic gives you more margin in sustained heat.
- Transmission fluid. Check the level and condition if your transmission has a dipstick. Healthy fluid is usually red or pink and doesn't smell burnt. Dark, burnt-smelling fluid is a sign to have it serviced.
- Coolant. Check the level in the overflow tank with the engine cold.
- Trailer wheel bearings. These get forgotten until one fails on the highway. Make sure they're greased. A quality grease built for wheel bearings is cheap insurance.
- Tires. Check the pressure on the truck and the trailer, using the numbers on the door sticker and the trailer tire sidewall.
On the road
- Use tow/haul mode if your truck has one. It changes shift points to keep the transmission out of overdrive hunting, which builds a lot of heat.
- Watch the gauges. If your truck shows transmission temperature, keep an eye on it on long climbs.
- Give it a minute. After a hard pull, idling for a minute before you shut down lets things cool a bit.
Built for the work
If you tow often, look at oils and fluids built for heavy-duty use. AMSOIL's synthetic transmission fluids are made to resist heat breakdown. Diesel pickup owners should look at diesel engine oil rated for the specification your engine requires.
Not sure which fluid your transmission takes? The vehicle lookup lists it by year, make and model, or send me the details and I'll look it up for you.
Questions about your vehicle or equipment?
Send Byron the year, make and model and he'll point you to the right products.