In the 1980s, GM introduced the 700-R4 overdrive transmission. This transmission has endured because of its simple design and retrofit capability. Today's cars largely have a set-it-and-forget-it overdrive transmission and seldom, if ever, is the overdrive turned off. This approach is less than ideal for the 700-R4 overdrive transmission, especially for tasks that require high performance. Following a few rules of overdrive use with this transmission can extend the life greatly of the unit.
Turn the overdrive off when driving in town. This transmission, in stock form, is an enterprise design that was used in just about anything equipped with rear-wheel drive. It had to satisfy a long family vacation drive as well as the cattle rancher pulling a trailer. There was no difference in the basic transmission build out. In stock form, shifting will become soft and sluggish and can chatter in and out of overdrive at low speeds.
Turn the overdrive on and off in hilly country, especially when towing a trailer. Turn the overdrive on when driving on flat roads and off when going up an incline. Overdrive is not enough to pull up a steep hill and the vehicle will slow until it shifts down automatically. The overdrive's design is not that strong and is engaged during normal driving. Undue stress shortens the life of the transmission.
Turn off overdrive when pulling a trailer and operate the gears manually. When the transmission is manually placed in second gear, an additional band is applied inside that prevents the transmission from shifting up. It also helps stop slipping. Use this feature to your advantage by applying brakes when traveling downhill.
Turn off overdrive in icy, wet weather. Throttling down the engine is a big advantage when conditions are prone to make the brakes lock and tires skid. Even though the engine will rev up, the transmission slows the car with internal gear brakes, making driving more ideal in inclement weather.
