Neglect

Neglect refers to inadequate routine maintenance - changing the transmission fluid, pan gasket and filter at regular intervals, checking for transmission leaks and checking the level and condition of the transmission fluid.

As the temperature of automatic transmission fluid rises, the chemical components start to break down. Over time, the lubricating properties of the fluid are diminished. If not replenished, transmission bearings and bushings begin to wear. If the bushings and bearings wear out, they can cause internal leaks which cause pressure losses, which lead to clutch, band and gear train failure. Regular automatic transmission fluid and filter changes (routine maintenance) must be performed to prevent the break down of automatic transmission fluid integrity.

In addition to the automatic transmission fluid losing its integrity, all automatic transmissions use rubber or paper gaskets and seals which shrink and become brittle when subjected to heat generated by the transmission. As this occurs, leaks develop. If these leaks are allowed to go unchecked, low fluid level will result. This will cause damage to internal transmission components. It is important to have a certified transmission technician regularly check your vehicle for transmission leaks.

Abuse

Any amount of extra weight on the vehicle that causes you to notice a difference in vehicle performance is approaching abuse. Excess heat caused by extra stress dramatically shortens the life of your vehicle's transmission. If the heat cannot be adequately dissipated, internal damage will result. In addition to the extra heat being generated, there's extra load on all of the internal components. Clutches and bands are designed to hold tightly under the load of the normal weight and horsepower of your vehicle. Increases in either of these will cause internal damage.

Avoid placing extra weight on your vehicle in such a way that you notice a difference in performance. For example, if your vehicle is not designed for towing, do not use it for towing.

Design Flaws

Some automatic transmissions have inherent design flaws that contribute to premature failure. For example, demand for comfortable shifting and the reduced weight of transmission components to conserve fuel, have contributed to premature wear inside the transmission. Most vehicle manufacturers have made great progress in improving transmission reliability over the last 10 years. They are more dependable today and last longer. But that doesn't mean they are flawless.

Normal wear and tear

Anything mechanical can, and will, at some point in time break down or wear out. Transmission failure is no exception. Bushings and bearings are usually the first components to go, with dynamically applied clutches and bands following. Dynamic meaning a band or clutch used to stop something in motion as opposed to preventing a stationary (static) object from starting to move. A reasonable service life can be from 40,000 - 50,000 miles up to 150,000 miles or more depending on the type of use. General family use on the high end. Fleet and commercial use on the low end.