How to Change Transmission Fluid

cross section of a transmission

Source I Vestman/Flickr

Doing a transmission fluid change is a DIY maintenance job that can save you money

A transmission fluid change might be a job you leave up to your trusted mechanic. Or you can learn to do it yourself in a few hours and save money in the process. If you're feeling like DIYing the job, we're here to help. Let's get you started.

When to change transmission fluid

Transmission fluid should be changed based on the vehicle manufacturer's recommendations. If you can't find that interval, every 30,000 miles is a safe bet. An automatic transmission that shifts roughly, slips or is noisy might also benefit from a transmission fluid change. A low fluid level can also cause these drivability issues, so check the level before you replace the fluid.

Vehicles that see severe usage such as towing or heavy hauling will need transmission fluid changes at an earlier interval; fluid that is darker than magenta and has a burnt-toast smell should definitely be changed.

How transmission fluid works

Your vehicle's transmission fluid performs two vital functions: lubrication and cleaning. As fluid circulates through various parts, it gathers and traps dirt and contaminants that can build up as the parts wear. Because of this, nothing adds longevity to a vehicle's life like regular fluid and filter changes. Automatic transmission fluid (ATF) is crucial to the operation of your automatic transmission. Different vehicles require specific types of ATF, so be sure to check your owner's manual for details before changing transmission fluids.

It's also important not to overfill the transmission. Overfilling means that the fluid can get aerated and whipped into a froth, and frothy transmission fluid can't do a good job of lubricating and cooling internal parts. It's also really, really important to be certain of what fluid your transmission needs. At one time, there was Mercon, Dexron, Dexron II, and Type F, and those were about the only formulations of transmission fluid on the market. Today, there are more than a dozen varieties of ATF, each with additive packages of detergents, friction modifiers, and other agents that are custom-designed for specific makes and models. Using the wrong fluid can quickly damage or even wreck a transmission.

Vehicle System
Fluids & Filters
Skill Level

This is a project that needs some know-how

Time to Complete
1-2 hours
  1. Prepare your work area for drips and spills. Wear gloves and safety glasses.

  2. Transmission fluid drains better when slightly warmed, so let your vehicle idle for a few minutes. Then, turn off your engine, and raise and secure the vehicle on jacks.

  3. Some vehicles have a transmission fluid drain plug, while others instead require the transmission pan to be removed. Place a drip pan under your transmission and either remove the drain plug or slowly remove the bolts on one side of the transmission pan.

    On vehicles with a drain plug, allow the fluid to drain for about 10 minutes and then reinstall and torque the drain plug to spec. Skip to Step 10.

  4. On vehicles with no drain plug, after removing the pan bolts on one side, slowly start to remove the rest of the bolts. Leave a couple of bolts in one corner loose, but don't remove them. The idea is to get the pan to tilt and drain from one side. Once the initial gush is complete, then you can remove the pan completely and allow it to finish draining. 

  5. Scrape off any old gasket material from the transmission pan mating surfaces. Then remove the old filter and O-ring. Prepare for more fluid! Take note of the filter mounting location.

  6. Automatic transmission filter kits usually contain a gasket and O-ring for filter sealing. Place the new filter onto the transmission in the same location as the old one. Make sure all surfaces are free of debris and all fluid passages line up correctly.

  7. After cleaning any debris out of the pan, install the new gasket using a thin film of oil-based grease to keep it attached. Keep an eye out for metal shavings or plastic particles, which can indicate transmission problems. Do not use adhesives.

  8. Lift the pan up onto the transmission and install bolts, finger-tight. Use a torque wrench and tighten the bolts to manufacturer's specifications in a criss-cross pattern. Tightening bolts in the right sequence is essential for a properly-seated gasket.

  9. Lift the pan up onto the transmission and install bolts, finger-tight. Use a torque wrench and tighten the bolts to manufacturer's specifications in a criss-cross pattern. Tightening bolts in the right sequence is essential for a properly-seated gasket.

  10. Safely lower the vehicle.

  11. Use the long funnel to fill your transmission with the recommended type and amount of fluid. On transmissions that don't have dipsticks, the fill opening will likely be on the side, and you may need to fit a hose between the funnel and fill opening. Or, to keep things simple and less messy, use this pump that attaches to the bottle. 

  12. Start the vehicle to check for leaks. Then let it run for a few minutes and cycle through all the gears. Then check the fluid level when the vehicle is warm, in neutral, and parked on level ground. Be sure to check for leaks periodically for the next couple of days.

  13. Pro Tip

    Always check your automatic transmission fluid with the parking brake securely applied and follow your owner’s manual instructions.

Last updated November 6, 2019