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How long do transmissions last?

Transmission Maintenance

Maintenance schedules offered by car manufacturers always include the transmission. As stated earlier, transmission fluid plays a critical role in how a transmission functions and the car part longevity. Like engine oil, transmission fluid should be checked and changed on a regular basis; however, the interval is different for all vehicles and dependent on the transmission and fluid type as well as use.

Most experts feel severe use warrants a recommended 15,000-mile (24,140-kilometer) fluid and filter change interval. Severe use is defined as more than 50 percent use in heavy city traffic with ambient temperatures above 90 degrees Fahrenheit (32.2 degrees Celsius) Remember the correlation between heat and lifespan? Experts also recommend changing the fluid whenever there is an indication of oxidization or contamination. Some transmissions, including a few models used by General Motors (GM), use an aluminum valve body. This soft metal is less tolerant of dirt and abrasives and GM recommends more frequent fluid changes to prolong the life of this auto part.

Changing transmission fluid is not as simple as changing engine oil and should be handled by a service technician or someone with a thorough understanding of transmissions. Generally, the car is lifted on a hoist, the pan is dropped and the old fluid pours out. This fluid and the pan are inspected for contaminants, such as fiber from clutch discs or any other indication of a larger issue that may be appearing. After a routine check of the exposed components the filter is changed, the pan is replaced and the fluid added to the proper level.


While periodic fluid changes are ideal, checking the fluid level and condition on a regular basis is a good idea as well. Most automatic transmissions have a dipstick similar to the engine oil dipstick. However, unlike engine oil, the car must be running to check the level. The vehicle manual will also specify if the car should be in park or neutral, and what temperature the transmission should be -- fluids expand with temperature and checking a cold transmission will often provide a false reading. When the dipstick is out, smell the fluid and note if it smells burned (a symptom of overheating), or like any other fluid (gas, coolant or motor oil), which may be a symptom of a leak in the system or contamination. Also, wipe some of the fluid onto a piece of white paper or cloth and check the color against a fresh fluid sample. Too much variation in color could mean contamination or degradation of the fluid.


Some newer transmissions, including the Chrysler NAG1, don't offer dipsticks for routine checks. Instead a technician has a special dipstick used in conjunction with a chart and an electronic scan of the transmission temperature to determine the proper level. Other manufacturers, including GM, have sealed transmissions that are only serviceable by trained technicians with the correct tools.


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