How to Change Transmission Fluid in Your Own Garage

Change transmission fluid at the recommended manufacturer suggested intervals.
Change transmission fluid at the recommended manufacturer suggested intervals. | Source

Failing to change transmission fluid on time will shorten your transmission service life and lead to early failure. This can represent a major expense and seriously hurt your economy. Fortunately, you can avoid this problem by replacing the fluid yourself. You spend much less for the service, and you can do it right in your own garage.

Professional car technicians know that:

  • Transmission fluid works hard to help transfer engine rotating power to the wheels every single mile you drive while keeping the system as clean as possible.
  • During this process, bands, clutches, gear sets and other components inside the transmission clash, push, pull and rotate at high speeds, releasing metal, dust, and friction material into the oil.
  • These particles accumulate, degrading the oil's lubricating, cooling and cleaning properties.
  • If you don't flush these particles and replenish you transmission with fresh oil, particles and worn oil will start to accelerate components wear.

So, even if your car manufacturer says your transmission fluid is good for the life of your car, it's a good idea to replace the fluid at least every 60,000 miles. Otherwise, follow the schedule in your car owner's manual or vehicle repair manual. Most likely, you can do this job yourself in your own garage using a few common tools.

Usually, you need to drop the oil pan from the bottom of the transmission to drain the oil and change the oil filter. A few models provide a draining plug on the pan and perhaps a separate compartment to access the filter, saving you a lot of work. But not all of them.

This guide will help you through the process to avoid transmission damage and leaks.

After miles of service, transmission fluid fills with dust, metal shavings, and other harmful particles that need to be flushed.
After miles of service, transmission fluid fills with dust, metal shavings, and other harmful particles that need to be flushed. | Source

Before you start, make sure you have the recommended type — and amount — of transmission oil, pan gasket, and transmission filter for your particular make/model/year vehicle. Check your car repair manual, which has a more complete list of parts, tools and other specifications you'll need to service your particular transmission. The manual will also tell you which components, if any, you need to remove to gain access to the transmission oil pan.

If you don't have the repair manual for your particular vehicle make and model, buy an aftermarket copy. They cost just a few dollars and come with a lot of useful information you'll need for other maintenance and common repair projects. You can buy a copy at most auto parts stores in your area or online.

Next, you'll find the steps you'll need to take for this project, with special emphasis on those details you have to pay attention to when changing the transmission fluid at home.

Tools you'll need:
chemical-resistant gloves
ratchet extension
set of sockets
torque wrench — borrow one from your local auto parts store, if necessary.
large (2 gallons or more) drain pan
flat-head screwdriver
shop rags
lint-free towels
plastic or dull scraper
hammer, if necessary
long-neck funnel
torque wrench

Getting Your Transmission Ready

Before you start, warm up the car to raise the transmission fluid's temperature. This will prepare your transmission for the job.

1. Idle the engine for about 20 minutes or take your car for a 15 minute ride so the oil in the transmission picks up all the loose particles that have settled around components. This way, the oil will flush these particles when drained.

2. Back at home, choose a level surface to park your car and turn off the engine.

3. Lift the front of your car using a floor jack and support it on jack stands.

4. Block the rear wheels using a pair of wooden blocks and set the emergency brake.

Draining the Transmission Oil

1. Put on your goggles and chemical resistant gloves.

2. Crawl under your vehicle and place the drain pan under the transmission oil pan and begin to loosen the bolts that secure the pan to the transmission using the ratchet, ratchet extension and socket.

3. Remove the bolts on the sides and front of the pan first. Leave the bolts on the back loose so that you can drain as much oil as possible before removing the pan completely.

Be careful when loosening the bolts as hot transmission oil will begin to flow out of the pan and you can burn your hands.

4. Tilt the pan to drain as much oil as possible before removing the pan. You may need to brake the seal between pan and the transmission using the scraper or screwdriver and hammer. Do this carefully to avoid damaging the mating surfaces.

5. Finally, hold the pan with a shop rage and remove the rest of the bolts.

6. Lower the pan slowly on a level position and gradually tilt the pan over the catch pan to finish draining the rest of the oil.

7. Examine the oil pan and particle magnet inside. A small amount of metal shavings is normal. If you find a large amount of shavings or small pieces of other foreign matter, this may indicate the transmission need a special service or some damage has occurred. If necessary, take the pan to a professional transmission shop so that you can get a professional opinion.

8. Place the pan and mounting bolts in a safe place for now.

9. Remove the transmission filter. The filter is either press fitted or bolted to the underside of the transmission. Carefully pull the filter right off the transmission or remove the mounting bolts using a screwdriver.

10. Some torque converters — the doughnut shaped device between the transmission and engine — have a drain plug you can remove to drain the oil inside as well. Check your vehicle service manual, if necessary.

11. Using a plastic or dull scraper, remove traces of the old gasket from the transmission and oil pan mating surfaces.

12. Thoroughly clean the pan and mating surfaces on the pan and transmission. Spray some carburetor cleaner on a lint-free towel and use the towel to clean and wipe the surfaces.

Some torque converters come with their own fluid draining plug to replace the oil inside.
Some torque converters come with their own fluid draining plug to replace the oil inside. | Source

Installing the New Filter and Pan

1. Compare the old filter to the new one to make sure you have the correct filter and install it.

2. Before placing the new gasket on the transmission pan, check your vehicle repair manual and see if you need to apply sealer to the new gasket. Sealer not only helps to seal the pan to the transmission, but helps hold the gasket in place during installation. Otherwise, you can use oil-soluble grease to hold the gasket in place, if necessary.

3. When ready, position the oil pan in place under the transmission. Hold the pan with one hand and begin to install the pan bolts finger tight using your free hand.

4. After installing all the bolts, tighten them gradually in three steps, following a crisscross pattern and a torque wrench.

  • Usually, you first tighten the bolts to half their final torque.
  • Then, tighten the bolts to three fourths of their required torque.
  • And finally, tighten the bolts to the manufacturer specifications. Do this twice to make sure the bolts are tightened to the correct torque — check your repair manual for the specified torque.

Make sure to add the correct type and amount of fluid you need for your transmission.
Make sure to add the correct type and amount of fluid you need for your transmission. | Source

Refilling the Transmission

1. After installing the oil pan, lower your car and wait for the sealer to dry, according to the manufacturer instructions, if necessary.

2. Refill the transmission with the correct amount and type of transmission oil recommended by your car manufacturer — check your car owner's manual or repair manual. Pour the oil through the transmission dipstick tube using a long neck funnel.

3. Then, replace the dipstick and start the engine. Warm up the engine; then, shut it off and check the pan for leaks. Fix any problems as necessary.

4. Now, start and idle the engine for about 15 minutes to bring the transmission fluid to operating temperature. Shift the transmission stick through the gears and back to Park.

5. Check the transmission fluid level and add as necessary. Then, shut off the engine.

To change transmission fluid you may need a couple of hours or more. But it's a maintenance job you can do at home for most vehicle models. This is an excellent project that helps you service the transmission according to your manufacturer's schedule at a fraction of the cost than you'd normally pay in a regular shop. But to keep your transmission working properly, check the fluid level and condition between changes and replace it as necessary.

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