Making Automatic Transmissions Last

With today’s automobile engines lasting 200,000 miles or more when properly serviced, how come so many transmissions are still dying early in the game? It’s estimated that over 13 million automatic transmissions fail every year, and $2,000 or more for repair is not unusual. Many of us remember the older vehicles that frequently went 150,000 miles without even a single service. These were the cars with plenty of room underneath them for a large heavy duty transmission that was under the vehicle rather than in the engine compartment.

Today, in the interest of curbing air pollution and increasing efficiency and fuel mileage, the transmission has been downsized and is usually in the engine compartment. Engines are designed to run at over 200 degrees, Air Conditioning has become standard, electric radiator fans only come on when they are really necessary and wind tunnel-designed bodies reduce air flow over the running gear (say transmission.)

The Automatic Transmission Rebuilders Association estimates that 90% of all transmission failures are due to transmission and transmission fluid overheating. The oxidation rate (which determines the useful lubrication life) of automatic transmission fluid doubles for every 20 degrees F. temperature increase over the normal operating level. This means fluid that’s formulated to last 100,000 miles at 175 degrees F. will only go 50,000 at 195 degrees F., or a mere 3,000 miles at 275 degrees F. Oxidized transmission fluid does not lubricate the transmission properly and leads to early failure.

Frequent servicing of the transmission can extend your Automatic Transmission’s life dramatically. The recommend servicing interval for the type of driving normally encountered by the average driver is every 30,000 miles. Vehicles that do excessive stop and go driving or towing should be more often. Transmission coolers are also recommended for any vehicle towing often or anytime towing heavy loads. Once the transmission fluid becomes oxidized, a flush is recommended, since under normal servicing only about 50% of the fluid can be drained out.