Does your vehicle have an automatic transmission? If so, it requires transmission fluid to operate properly. Also known as ATF, that fluid prevents the transmission from running too hot, especially when your vehicle is towing a trailer, climbing steep hills, or operating under any other severe conditions.
Like all automotive fluids, transmission fluid will break down and become less effective as it ages. When it gets too hot, the fluid will oxidize, turn brown and start to smell like burnt toast. Intense heat will also affect the fluid's ability to do its job. Varnish will form on the valve body and other internal parts, which will affect the transmission's functionality.
If the temperature climbs too high, the rubber seals within the transmission will harden and break, allowing leaks and a loss of pressure. And if the clutches burn out the only option is a complete overhaul, which can get pricey.
Your transmission is your vehicle's most complex system. Repairing or replacing it can be expensive. That's why it pays to take good care of it. So, have your transmission fluid and filter checked every 30,000 miles. The fluid may only need to be changed every 60,000 to 100,000 miles, though. If you put your car or truck through more stress than the average driver, have the transmission inspected and serviced more often to prevent it from overheating.