How To Change Manual and Automatic Transmission Fluid

Replacing a Filter and Fluids

Image of a car engine

Transmission fluid is required to lubricate and cool the transmission components. If you want your transmission to last for a long time, then you are going to have to change the fluid and filter at regular intervals. Old, worn-out fluid doesn't work as well, and clogged filters are much less efficient. New fluid is bright red, old fluids are a much darker red--almost black.

Many people wonder how often they should change their transmission fluid. Automatic transmission fluid and filters should be changed every 15,000 to 30,000 miles (or every 2 years) as part of your basic car maintenance. It's important to change both the filter and the fluid at each interval. Don't wait until the transmission begins to slip. 

Here's how to change your transmission fluid.

  1. Preparation: Go buy the correct fluid at an auto supply store. Your owner's manual should indicate the correct type of fluid for your car. Also, get a new filter.
  2. Tools: Here's a list of all the tools you should need:
    1. Floor jack - to lift the car
    2. Jack stands - to hold the car up while you're working
    3. Drain pan - it should be big enough to hold at least 5 quarts
    4. Newspaper
    5. Clean shop rags
  3. Block the tires, and set the emergency brake.
  4. Remove one of the transmission cooling lines running to the radiator. Connect a tube to the end of the line, and place the end of the tube in a drain pan. Start the car, and let it idle for a minute or two. Transmission fluid should flow out of the cooling line, through the tube, into a drain pan. Turn the engine off as soon as the fluid stops flowing.
  5. Raise the car with a jack. Use the jackstands. Do not put any part of your body beneath a vehicle unless it is properly supported.
  6. Now you need the drain pan again. Put it in place underneath the bottom of the transmission pan. Center it towards the front of the transmission. Put newspaper underneath the drain pan in case any fluid spills.
  7. Remove all but the rear bolts holding the pan tohow to change your transmission fluid the bottom of the transmission. Loosen the rear bolts last. Only loosen them a few turns.
  8. If the pan hasn't lowered already, use a flat head screwdriver to separate the pan from the rest of the transmission. It should tilt so that fluid can flow out of the front end of the pan into the drain pan.
  9. When fluid stops coming out, take out the last few bolts at the rear, and lower the pan the rest of the way. Pour the remainder of the fluid into the drain pan.
  10. Remove the old gasket, and thoroughly clean the transmission pan with any type of solvent. Let it dry in a clean place.
  11. Pull the filter out of the transmission and replace it with the new filter
  12. Put a new gasket on the cleaned transmission pan, and place the pan on the bottom of the transmission. Insert the bolts and hand tighten them. Then use a wrench to tighten the bolts a little at a time. Try to tighten them evenly so that you don't bend the transmission pan.
  13. Remove the jackstands from the vehicle, and add the correct amount of fluid. Your owner's manual should tell you how much to add--usually about 7 pints.
  14. Now you can check your work. Start the engine and let it idle for a few minutes. Set the parking brake and shift between gears, then check the fluid level with the engine running. If the fluid is low, add a little at a time until the dipstick indicates a sufficient level of fluid.

Manual transmissions have far fewer moving parts and are much more robust, but most manufacturers say that they still require lubricant changes every 30,000 miles (or every 2 years). Changing the fluid on your manual transmission is a little easier than changing fluid in cars with an automatic transmission. It's very similar to changing your car's oil. Here's how to replace manual transmission fluid:

  1. Drive around the block a time or two in order to warm up the fluid.
  2. Lift your car with a good jack, and properly support it with jackstands.
  3. Place a drain pan beneath the drain plug on the transmission and use a wrench to remove the drain plug. The fluid should flow into the drain pan. Watch out! The fluid is hot! Once the fluid stops draining, put the plug back in and tighten it securely.
  4. It can be a little bit tricky adding fluid back into the transmission. There is a a plug about half way up the side of the a transmission. Remove it, and add fluid through the fill hole. There might not be enough space to hold a 1 quart bottle, so you might need to use an alternative method to refill the fluid. Some things that seem to work are small funnels, syringes, or specially designed pumps. Once the transmission fluid is added, put the bolt back on and tighten it securely.
  5. Lower the car, start the engine, and drive around the block. Carefully look for leaks around the drain plug and the fill plug. If you don't find a transmission leak, pat yourself on the back for a job well done.


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