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How Often to Change Transmission Fluid

Stephen Rampur
It is recommended to change the transmission fluid of a manual transmission vehicle after every 30,000 to 60,000 miles and that of an automatic transmission vehicle after every 30,000 miles or never, depending on the recommendation of your car provider.
Transmission fluid is the lubricating agent that acts as a coolant for the transmission system.

There are two types of transmission systems used in the vehicles namely, automatic transmission system and manual transmission system.
In automatic transmission, the driver needs to choose the gear he wants to drive in and the transmission will automatically shift. However, in manual transmission system, the driver needs to change the gear manually so that the force applied on the engine is balanced.
If the transmission fluid loses its properties, the entire transmission process may not be smooth and eventually the engine will be damaged. It may seem that there can be a fault in the transmission parts or some kind of a manufacturing defect.
However, if there is a trouble in the transmission system, the problem can also be due to not changing the transmission fluid on time.

What is Transmission Fluid?

Fresh transmission fluid is generally pink in color and is a clear liquid.

Transmission fluid is a liquid that lubricates the parts of the transmission system. The transmission system is nothing but the gearbox.
The transmission fluid transmits power from the engine to the transmission system. In the absence of this fluid, the transmission system would get stuck or you might hear certain sounds from it.
It also contributes to less heat generation from the transmission components, which eventually leads to less corrosive damage and more durability of the parts. If a transmission cooler is incorporated in the car, the fluid plays the role of a coolant.
Check the transmission fluid when the engine is running.

To change the fluid, it is necessary to know its position in your car. There is a dipstick handle located in the car's transmission system. This dipstick is located in the rear of the in-line engine in a rear wheel drive car.
In a front wheel drive one, the dipstick is in the transaxle. Check the fluid with a dipstick, if it has turned dark and has a burning odor, change it.
Changing Process

Typically, automatic transmission fluid is needed to be checked once in a month to avoid any serious complication, for which you may have to pay a huge sum.
You need to take due care in the periodic checking of the fluid, as getting the whole transmission set replaced is pretty expensive. The time intervals of changing the fluid differ according to the car company.
If the transmission fluid goes below the recommended level, there is a chance of leak. Take the vehicle to the mechanic immediately.

In case of manual transmission cars, the fluid is ideally changed every 30,000 to 60,000 mi. Some car companies suggest the fluid to be changed every 15,000 miles, in case the car is to be used for heavy work on a regular basis.
A few car manufacturers claim that the automatic transmission fluid need not be changed at all!
  • First step in the manual fluid change process is to park and jack up the car.
  • Locate the filter and unscrew the bolt properly using a wrench. Don't apply too much pressure as the bolt can get damaged. If the bolt is jammed, try using a gas torch to heat the bolt.
  • Similarly, remove the drain bolt as well. Drain bolt is located beneath the engine block near the engine crankshaft for vertical shaft engines and it is located below the centerline of crankshaft for horizontal shaft engines. Don't forget to place the drain pan under the bolt location.
  • Allow the entire transmission fluid to collect in the pan.
  • Now remove the filter, clean it properly and place it back. It is also necessary to clean the drain bolt as it might have metal shavings.
  • Once the entire fluid is drained out, tighten the drain bolt back in its position.
  • Now, add the oil back using an oil pump. Maintain the level of fluid as mentioned in the manufacturer's manual.

When to Change the Fluid?

Regular checks are necessary to know the level of transmission fluid. However, there are few other "symptoms" that indicate the need for fluid change.
  • There is a grinding sound or some strange sound when you drive the car.
  • Facing difficulty in changing gears.
  • Slipping of gears.
  • The vehicle starts to surge forwards or backwards.
  • The vehicle tends to stop for a few seconds before it shifts gears.

Transmission Flush - Is it Necessary?

Transmission flush is the process of completely flushing out the transmission fluid and replacing it with new fluid. There are many debates on whether the flush is necessary at all.
A few auto experts feel that the flushing process will only have positive effects on the transmission system, like improving its efficiency. However, a few others have different opinions. They recommend to simply fill the transmission fluid whenever it goes below the recommended level.
To avoid any confusion, look for the symptoms of fluid change. Follow the steps given below if the transmission fluid needs to be flushed.
  • First step is to jack the car.
  • Now, locate the transmission position and place the drain pan beneath the transmission.
  • Remove the drain bolt and let the entire fluid to collect in the pan.
  • Replace the bolt after cleaning it and fill oil in the transmission using an oil pump.
  • The next step will be to locate the return path of the transmission line which is located at the bottom of the radiator. This line will be connected to the cooler.
  • Disconnect the line and place it in a container to collect the fluid.
  • Now, start the vehicle and accelerate a bit. You will see fluid getting collected in the container. This is the old fluid that is still present in the vehicle even after the draining process.
  • Once the fluid is collected, turn off the engine and reconnect the transmission line.
  • Now, check the fluid level using the dipstick. If the level has reduced, add fluid to maintain the recommended level.

Popular Brands

If you choose to change the fluid at home, you can certainly save some money on the cost of flushing. If you take your car to a professional and get the fluid replaced, it might cost you somewhere between $75 and $250, according to the car make and model. The labor costs involved may differ as well, depending on the location.
For selecting the right transmission fluid for your car, it is recommended that you use the ones mentioned in your car's service manual. However, there are a few popular brands namely,
  • Red Line
  • Royal Purple
  • Lucas
  • Mobil
  • Lubegard
  • GM Synchromesh
  • Amsoil
Remember that checking the level of the fluid at regular intervals and changing the fluid when necessary, is one good way to keep the transmission system in a proper working state for a substantial period of time.