How to change automatic transmission fluid | Autoblog Wrenched

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Changing your own automatic transmission fluid should be done every 20,000 to 50,000 miles. Good thing it’s pretty easy! See how on this Autoblog Wrenched.

Watch all of our Autoblog Wrenched videos for more tips on how to diagnose, fix, and modify cars from professional detailer Larry Kosilla. While you’re at it, check out Larry’s other car cleaning and maintenance video series Autoblog Details!

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Instructions (video transcript):

[00:00:00] [Narrator] Changing your automatic transmission fluid is easy and should be performed every 20 to 50,000 miles for most vehicles that require a service, but check your owner’s manual to find out when it should be changed, what type of fluid is required, and how many quarts the system holds before you get started. Here are the tools you’ll need to do it yourself. Socket and torque wrench, brake clean, catch can, scrubbing pad, bucket, gasket adhesive, transmission fluid, gloves, safety glasses, basic tools, rags, and a funnel.

[00:00:30] I’m Larry Kosilla, pro-detailer and trainer for the last 15 years, but when it comes to what’s under the hood, I’m the student. Follow me as experts teach me how to diagnose, fix, and modify cars on Autoblog’s Wrenched. I’ve heard of quick lube places offering a transmission change, a service, and even a flush. What’s the difference between those two? – Well, a fluid change would be where you just drop the fluid out, you put fresh fluid on top. A service would be removing the pan,

[00:01:00] putting in a fresh filter, and then filling the fluid back in the top. A flush actually cleans the fluid out of the torque converter, which hold a few quarts of oil that you can’t drain by just taking the pan out, so one of the better ways to do it is if you put in fresh fluid, put in a new filter, drive it around for awhile, you’re dissipating a lot of the old fluid, mixing it in, then you drop that again. Now it’s hard because you have to do it twice, but it’s so easy you can actually do it yourself. – [Larry] Check the current fluid to get an idea of its condition, smell, color, and level.

[00:01:30] Use the same color paper towel now as you will later so you can compare the transmission fluids easily. Be sure to have an empty catch can before you start this process. With the car in the air, find the transmission and unscrew the drain plug or, in some cases, you’ll need to unscrew a few bolts on the pan and do what’s called a slow drain before removing them all to avoid a huge mess. Luckily, this car has a drain plug, which makes this process a lot easier.

[00:02:00] Now, with most of the fluid out, remove the transmission pan. With the pan out of the car, now it’s time to do some detailing. First, remove the previous gasket with a plastic razor blade or scrub pad, making sure not to gouge the flat surface, which might cause a future leak. Brake clean the pan inside and out, related bolts and pay special attention to the magnet filter. Much like oil drain plugs, transmissions have magnets, as well, attached to the inside of the pan

[00:02:30] to attract metal shavings from the transmission during its use. It’s scary to see all the metal pieces, but I’m told it’s completely normal. Look at the transmission mating surface and make sure this is as clean as the pan. This is an extremely important step for a perfect seal, so it shouldn’t feel rough or bumpy, or have any leftover gasket residue. Now that everything is clean and ready to go, it’s time to replace the filter, but it’s a good idea to make sure the old one and the new one are exactly the same.

[00:03:00] Most filters will have a rubber gasket, like this one here. Add new transmission fluid to the rubber for a better seal prior to installing and torquing. Next, reinstall the pan, but a new gasket is needed to replace the old one we scraped off. Before adding a new gasket, a sticky gasket adhesive is placed on the mating surface to hold the gasket in place during the re-installation to avoid it moving or sliding and possibly causing a leak down the road. Now carefully install the pan while trying to avoid moving the gasket,

[00:03:30] then hand tighten all the freshly cleaned bolts. Once the pan bolts are hand snug, torque them in a criss-cross pattern to evenly crush the gasket, much the same as torquing your lug nuts. In this case, it’s just a few more bolts. If you’re wondering where to find the torque specs for your car, you can easily check online or with your local dealer. Take the old fluid in your previously empty catch can and pour it into an old gallon or quart container to measure exactly how much was removed from the tranny.

[00:04:00] Be sure to properly dispose of the spent fluid. This is toxic and must be disposed of properly. Check your local auto parts store to see if they recycle or can recommend where to go. Add your funnel to the dipstick tube, and replace the same amount of old fluid, but with new fluid. Next, start the car, and with your foot on the brake, go through the gears to help flush the clean fluid through the torque converter, which will squeeze out the old fluid that was once trapped and left behind even after our first drain.

[00:04:30] Now with the car turned off, go back to the drain plug and drain the fluid once again without removing the pan. You’ll see the clean fluid we put in just a few minutes ago mixed with the old, and now has turned everything a little bit darker, but it’s definitely better than our old or original fluid we once had in the car. Now repeat the last step by adding the same amount that was removed like we did before. Afterwards, start the car, run through the gears again,

[00:05:00] and top off the fluid as required. Most cars need to be running in idle for the dipstick reading to be accurate, but check your manual to be sure. Likewise, make sure your car is on a flat or even surface to avoid a false dipstick measurement. So here’s what I’ve learned. When changing your fluid, you really only get about 50% of the old fluid out because the rest is trapped in the intricate maze that is your transmission. Number two, make sure you use the exact spec fluid for your transmission found in your manual

[00:05:30] or you may cause premature wearing. Number three, having a drain plug is necessary to complete our compromise between a simple change and our DIY flush as we did in this video. And lastly, if you decide to go to a professional, understand the difference between a change and a flush. Make sure your mechanic is aware that you know the difference between the two services, how many quarts your tranny holds, if he’s changing the filter, and of course, if that’s included in the price. For more how-to car repair videos, visit autoblog.com/wrenched.

[00:06:00] I’m Larry Kosilla from ammonyc.com. As always, thanks for watching.