Automatic Transmission Maintenance

The automatic transmission is one of the most complicated and vulnerable plus one of the less reliable parts of any vehicle. The repair of an automatic transmission is often complex and very expensive. Automatic transmission problem can even make your car unsafe to drive - some transmission defects, for example, may cause the car to stall, imagine the car that you are driving stalled while on a steep hill climb. Damaged auto transmission can also cause car to roll with the transmission in Park or even drive forward in Neutral. On the other hand, with good care your transmission can last longer.


What can damage your automatic transmission


Most of the transmission troubles start from overheating.
Under heavy load, such as towing a heavy trailer, rocking the vehicle from the snow, having continuous stop and go traffic in hot weather, racing, agressive driving and constatly down shifting etc. the transmission overheats. At higher temperatures the transmission fluid burns, losing its lubricating qualities and becomes oxidized leaving deposits all over inside the transmission. Exposed to the heat the rubber seals and gaskets inside the transmission become hardened causing leaks. The metal parts warp and lose their strength. All this, sooner or later, results in transmission failure. For example, a friend of mine burned the transmission when he was spinning the wheels too hard trying to free his shiny Audi from the snow on the next day after he bought it!
However, overheating is not the only reason - sometimes transmission breaks down because of poor design, due to lack of maintenance or after being rebuilt by inexperienced technician. Few other reasons: harsh driving, too low or too high transmission fluid level or wrong transmission fluid type - a person I know added gear oil into the automatic transmission... guess what happen, the transmission died after 40 minutes of driving! 

How to prevent the transmission from damage


- Regularly check your parking space for leaks. Doesn't matter, is it the engine oil leak, power steering fluid or transmission fluid; if you discover any, get it fixed before it caused something serious.
- Once a week, check the transmission fluid level and condition. Not all cars however have the automatic transmission dipstick, in some cars, for example, in late Volkswagen models, the transmission fluid can only be checked by the dealer. Consult with your owner's manual for details. If the transmission fluid level is too low, there is a leak somewhere that needs to be fixed. 
- Change the fluid as often as it said in your owner's manual or when it becomes too dark (rather brown than red) or dirty.
Also, keep in mind that an automatic transmission can not be drained completely - there is always some transmission fluid left inside the transmission (the torque converter, in the valve body, etc.) which means you only can change about %60 of the fluid at once. This is one more reason to change it more often. 
- Use only the same type of the transmission fluid as specified in the owner's manual or on the dipstick. Many newer vehicles are very sensitive to fluid type. For example, an Owner's Manual for 2008 Honda Civic says "Using transmission fluid other than Honda Genuine ATF-Z1 may cause deterioration in transmission operation and durability, and could result in damage to the transmission".
- Never shift to the Reverse or Park until the car comes to a complete stop.
- Never shift from the Park to other gears when engine rpm is higher than normal idle.
- In many cars, the automatic transmission can be damaged if towing with the drive wheels on the road. Check your owner's manual for the proper way of towing your car.
- You can also install an aftermarket oil cooling kit to keep the lubricating temperature down if you have an aggressive driving pattern.

Refer to Your Car User's Manual to Determine What ATF to use

How to use overdrive


Generally speaking, overdrive (O/D) is the highest gear in the transmission. On most cars the automatic transmission has 3 speeds and Overdrive (forth speed). Overdrive allows the engine to have less rpm with higher speed in order to have better fuel efficiency. When you switch it on, you allow the transmission to shift into overdrive mode after the certain speed is reached (usually 30 - 40 mph depending on the load). When it's off, you limit transmission shifting by third speed.
In normal driving condition the overdrive should be always on.
You may need to switch it off when driving in mountainous area or towing a trailer.
[The automatic transmission automatically shifts from OD to the 3-th gear when it feel more load. When it feels less load it shifts back to the O/D, but under certain conditions, e.g.: driving uphill or towing a trailer, the transmission can not decide to stay in OD or to shift into 3-th speed and it starts to shift back and forth. That's the time you may switch it off and help the transmission to decide.] .
You also may need to switch it off when you want to slowdown using the engine braking, for example, driving downhill. [For more details, check your owner's manual]

AfterMarket Oil Cooler Kit

Servicing your transmission


I'd recommend to go for a service to your car make dealer - they have original parts, they know exactly what type of the fluid to use and their technicians are highly trained to service particular vehicle model. Even if you go to the independent garage, always ask to use original parts - sometimes, the after-market parts are not of as good quality as original.