Learn about Transmission Service & Maintenance

Learn about Transmission Service and Maintenance


Transmission Service and Maintenance schedules offered by car manufacturers should include the transmission. Car owners beware: Many manufactures such as BMW, Lexus, Nissan, Mercedes, Audi, and now, Cadillac, state that their transmissions have lifetime fluid. Lifetime, in car speak translates to “life of the warranty.” Their transmissions should still be serviced at least every 40,000-60,000 miles. 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 20,000-30,000 mile fluid and filter change interval. Severe use is defined as more than 50 percent use in heavy city traffic or with ambient temperatures above 90 degrees Fahrenheit, we also recommend changing the fluid whenever there is an indication of oxidization or contamination. Most modern transmissions, including ZF models used by GM, BMW, Audi, Porsche, and Mercedes-Benz use an aluminum valve body and magnesium housing. 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.

In the old days, generally, the car was lifted on a hoist, the transmission pan was dropped and the old fluid pours out. The 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. In modern times, 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. Modern cars and luxury vehicles have complex computer controlled transmissions that require using diagnostics systems to communicate with them and special functions and procedures for the service. Any fluid remaining in the torque converter and other parts of the transmission should be flushed using a special machine.

Manual transmission fluid change is usually simpler. Manual transmissions are usually outfitted with drain and fill plugs. The car is lifted, the oil drained, and then refilled with the proper grade specified by the manufacturer. If an owner decides to tackle this operation on his or her own, one thing to remember is to make sure the fill plug can be removed and the fill tube is clear before draining.

While periodic fluid changes are ideal, checking the fluid level and condition on a regular basis is a good idea as well. Older automatic transmissions have a dipstick similar to the engine oil dipstick. Modern transmissions can only have the fluid level checked with manufacturer specific electronic scan tools. However, unlike engine oil, the car must be running to check the level. The vehicle manual may 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.

Manual transmissions can be checked by opening the filler plug. The level should be just below this hole. Dip a cotton swab in, pull some fluid out, and smell it to check the condition of the oil just as you would on an automatic transmission.

While maintenance is key to auto part longevity, hard shifts, delayed shifting, being aware of any bangs, whines or groans from the transmission, as well as smells, will help head off any problems at an early stage.

To schedule an appointment for auto repair, service, and auto performance products and upgrades please contact service@sprint-motorsports.com or 408-831-3730. We welcome you to stop by our shop at 2099 S 10th St  Unit 40 in San Jose, Ca.  If you have any questions about your auto’s performance or maintenance, don’t be shy about asking our friendly staff for assistance.