Changing Your Automatic Transmission Fluid

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By Courtney Evans  2 wrench difficulty 2money

Automatic Transmission Shift Lever

Automatic Transmission Shift Lever

You’re driving to work this morning and you’re thinking about the day ahead.  “I wonder if I’m going to finish that project”, “I sure hope that I don’t have to deal with that smart@ss IT guy today”, “I can’t wait to have my coffee, discuss the game with Mike, and collect my $50″.  Life is good.  All of a sudden, you hear your engine “surge”, yet you didn’t press harder on the accelerator.  You did notice your engine holding first gear a little longer than usual when you pull out of the driveway earlier but you thought nothing of it.  What gives?  Uh-oh, something is going on with your automatic transmission.  Now you feel a “surge” of your own.  A surge of dread as you think of all the greenbacks your going to have to shell out to repair your transmission.

The previous scenario is very common.  Especially for those that show no love for their automatic transmission.  This system of gears, switches, and fluid is probably one of the most under appreciated systems in the vehicles of those who prefer not to manually row their own gears.  The automatic transmission is an engineering marvel that goes along about its business without any major decisions or input from you.  Out of sight, out of mind.  As with all vehicle systems, a little TLC is required.  The most important requirements are checking the fluid level and changing the fluid.

The best policy when it comes to  most automotive issues is…wait for it…prevention.  So, let’s turn the Way back Machine to a point in time where you could have prevented the scenario above.  Let’s see if I can get you through changing the fluid.

Overall, the procedure is rather simple and should be done every 30,000 miles.  We’ll cover checking and changing your automatic transmission fluid now.

Use your senses
The first logical step is to check the fluid level.  With the engine warm, the gearshift selector in Neutral, and the engine idling, pull out the transmission fluid dipstick and observe.  The fluid level should be somewhere between the marks “Add” and “Full”.  The difference between these levels is only about a pint of automatic transmission fluid (ATF).  A simple top-off of the fluid might fix your problem, if you’re lucky.  A continuously low reading could indicate a leak somewhere in the system and requires further investigation.


Let’s look at the condition of the fluid.  The ATF should be bright red in color and should be clear.  It should resemble strawberry syrup.  You know, like the syrup that you had on your strawberry sundae last night.  Yeah, like that.  I bet you’ll never look at a banana split the same way again!  The fluid should smell sweet as well.  It probably tastes awful and is poisonous too so, don’t lick the dipstick.  If the fluid is dark, smoky, and has a burned smell, a fluid change is in order.  So, when it comes to ATF, strawberry syrup good, chocolate syrup bad.

Out with the old
First, you need to safely get your vehicle up on jack stands or ramps.   Make sure that you chock the wheels to prevent the vehicle from moving.  Find the location of your transmission pan.  It will be a pan that looks similar to your oil pan with bolts around its perimeter.  Consult your owner’s or service manual for the location.  Now, if you were to just start unbolting the pan, while leaving a few bolts partway in, the ATF would begin to flow out around the seam and splash outside the radius of your catch pan, making a big mess.  So, a better idea would be to remove as much ATF as possible before unbolting the pan to gain access to the filter.  Yes, there is a filter that needs to be changed as well.

If you have a fluid extraction tool, use it to pull as much fluid out of the system as possible through the dipstick tube.  To extract even more of the old ATF, leave the pan on and remove one of the transmission cooler lines at the bottom of the radiator.  Make sure that you put a drain pan underneath it and start the engine for a few seconds to find the direction flow of the fluid.  The flow direction doesn’t matter, but you have to connect a small hose to the radiator outlet or the line connector to collect the old ATF.  If you really want to be thorough, you can poor in a few quarts of fresh fluid into the dipstick tube at about the same rate as the old fluid coming out to create a flushing effect.

Changing the filter
Once you’ve removed as much fluid as possible, you can remove the pan.  You have to remove the pan to gain access to the transmission fluid filter.  This also must be done so that you can wash out any accumulated sediment or solids.  Remove the filter.  You may have to loosen a few screws.  Taking a close look at the filter will help you determine the general health of your transmission.  There should be hardly any debris in a transmission that’s healthy and has had its first change.  Anything beyond that is an indication of a developing problem.
Insert your new filter.  Some filters are tubular and some are flat.  Make sure that you replace any O-rings that you find on the neck of your filter.  They will be included in your kit.  You should have a new transmission pan gasket from the kit as well.  Be sure to remove any of the old gasket to ensure a proper seal of the new gasket.  Start every pan bolt by hand at first and then use a cross pattern for tightening all the bolts.  If the gasket is made of cork, you can use a thin layer of gasket sealer to hold it in place while you’re trying to start the first couple of bolts.

In with the new
Now that the old fluid has been removed and the new filter and pan gasket have been installed, you can fill the system with new ATF  through the dipstick tube.  Make sure that you consult your owner’s or service manual to determine the amount of ATF that you need.  Also, make sure that you have the recommended type of ATF, per your owner’s manual.  Dexron III/Mercon ATF will work for most vehicles except 1992 or earlier Fords which require Type F, but again, check your manual.

Here’s quick procedure list

1.  Use your senses to observe the quality of you ATF
2.  Properly raise your vehicle to gain access underneath
3.  Remove all of the old ATF
4.  Remove the filter and clean the transmission pan
5.  Reinstall the new filter and gasket
6.  Top off with new ATF

Changing your automatic transmission fluid is a procedure that requires a little time and a little patience and can easily be completed on a weekend day.  Being proactive when it comes to your transmission will pay lots of dividends in the future.  Check your ATF fluid often to head off any problems and prevent both types of “surges”.  If you have to drive to work, at least enjoy your drive.



1 Comment:

  • By What You Need to Know About Your Vehicle's Filters 12 Nov 2013

    [...] The task of changing the fluid and filter can be quite involving but definitely within the ability of the do-it-yourselfer.  For more detailed information on the process of changing your automatic transmission fluid and filter, refer to the issue “Changing Your Automatic Transmission Fluid“. [...]

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