How To Change Your Automatic Transmission Fluid

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The fluid in your car’s automatic  transmission serves a few purposes. It lubricates the inner workings of the transmission and it acts as a coolant. Most importantly of all, the fluid, under pressure, controls the clutch via the hydraulic action of the transmission’s torque converter.

An automatic transmission is very complex and it’s worth taking the time to make sure it’s maintained properly.  Opinions vary from one car manufacturer to another on how to service their automatic transmission and if the fluid needs to be changed. Some say to change the fluid every 30,000 to 60,000 miles. Surprisingly enough, others will say it never needs changing. It can be confusing but the best bet is to check your owner’s manual or a dealer service centre.
Learn the correct way to check your car's automatic transmission fluid
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Learn the correct way to check your car's automatic transmission fluid
This is a typical automatic transmission dipstick
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This is a typical automatic transmission dipstick

Let’s begin by checking the level of the transmission fluid. Much like your car’s engine oil, there is a dipstick to check it. Car manufacturers have got better about making the dipstick easy to find. It may be a red colour which matches the colour of the fluid or it will be clearly labelled. 
The next step is important. Check your owner’s manual for the correct way to check the level of your transmission fluid. Some car makers want the car’s engine running, with the transmission in park or neutral. Others are fine with it warmed to running temperature. Once you have done that, then pull out the dipstick and check the level. If the fluid is clean and red, it doesn’t need changing. If it’s low, merely add some fluid with a funnel into the hole where you pulled the dipstick.
This is a transmission pan with a drain plug
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This is a transmission pan with a drain plug

If the fluid is dark and muddy looking, then it’s time to change it. But let’s get down to some basic information first. Begin by finding out how to drain the transmission fluid in your car. Is there a drain plug or do you have to remove the fluid or transmission pan? Next, you need to know with a fluid drain you are not draining all of the old fluid. With some transmissions, you may only drain 50% of it. The upside, of course, is you are draining a good portion of the old fluid and replacing it with new, which is much better than where you started. To replace all of the fluid, it requires a flush which won’t be covered with this guide.
To make it easier, you can purchase gasket and filter kits
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To make it easier, you can purchase gasket and filter kits

Draining the fluid via a drain plug sounds easy and it is. But it may be worthwhile to remove the transmission pan. The fluid  filter may be located in the pan as well as a magnet which attracts metal particles and flakes from the transmission. With the pan off it gives you the opportunity to change the filter, clean the magnet and replace the old pan  gasket. In addition, if there are large metal pieces in the pan or on the magnet, you should get your transmission checked at a transmission shop immediately. With all of that out of the way, let’s begin by draining the fluid.
Purchase a large drain pan to hold all of the fluid
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Purchase a large drain pan to hold all of the fluid

Out With the Old - Draining the Fluid

Before you begin, have a drain pan ready. Your typical passenger car’s transmission holds about 13 litres of fluid. This will, of course, vary on the make and model of your car or van. To put it simply, get a large drain pan to be safe.
Ratcheting wrenches work great when removing drain plugs.
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Ratcheting wrenches work great when removing drain plugs.

With the drain pan under the drain plug, you can unscrew and remove it. A closed box or ratcheting box end  wrench works great in this situation. Allow as much of the fluid to drain as possible. Since you are not doing a full flush, give the fluid some time to drain. This way, you will be replacing as much of the old fluid as possible.
Safety glasses and rubber shop gloves are good protection from the transmission fluid
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Safety glasses and rubber shop gloves are good protection from the transmission fluid
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Safety glasses and rubber shop gloves are good protection from the transmission fluid

If you have to remove the transmission pan, it will be a little messier. As you loosen the bolts holding the pan to the transmission, the fluid will run out from all sides of it. To be safe, wear safety glasses and rubber gloves.
Make sure you use the correct fluid for your car
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Make sure you use the correct fluid for your car

In with the new - Refilling the fluid

An important step to this whole process is having new fluid ready before draining the old. Make sure you check your owner’s manual or your dealer service centre to find out the correct transmission  fluid for car. There are a few different kinds of fluid and you need to be sure you have the correct one for your transmission. 
Next, with the fluid drained, make sure the drain plug or the bolts for the pan are clean. Then either screw the drain plug back into the transmission pan or, if you had to remove the whole pan, bolt it back onto the bottom of the transmission. Don’t use too much torque when tightening the bolts. You don’t need to strip the drain plug or crush the pan gasket.
Long neck funnels help refill the transmission fluid
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Long neck funnels help refill the transmission fluid
With most cars and vans, the transmission dipstick port doubles as both the place to check the fluid level and to fill the transmission with new fluid. With a long neck   funnel, insert it into the dipstick port and slowly fill it with new fluid. The new fluid you add will vary based on what’s recommended for your car. You don’t want to overfill it. After checking it and you come up short, you can always add some to get it to the correct level. Remember to use the correct procedure for your car when checking the fluid level.

And finally, please dispose of your old transmission fluid properly. Most car part shops provide oil recycling services to their customers for free. Just ask and they will usually direct you to a large storage tank where you can dispose of your old fluid. With that taken care of, you can claim another successful do-it-yourself project to your car.
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Written by:  ridestory
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