You are obsessed with motor oil. This is normal. The engine is the heart of the car. Power is transmitted through the crankshaft, pistons and wheels. It absorbs all the energy and sends it to the pavement. If you ignore your transmission fluid, you’re in trouble. The liquid is usually magenta in color. Covers all the equipment inside the case. It acts as a hydraulic medium. This change in fluid pressure determines when the gears shift. It’s more than just lubrication. This is the lifeblood of your transmission.
Most cars on the road use an automatic transmission. Automatic transmission fluid (ATF) is required. Regular driving from home to work can raise temperatures. The temperature of the liquid reaches 175 degrees Fahrenheit (79 degrees Celsius). This is not a malfunction. This is normal. At this temperature, ATF will last about 100,000 miles (160,934 kilometers). It goes on and on. Like the energizer bunny.
But the temperature rarely stays at 175 degrees. Stop-and-go traffic. Tow heavy loads. Mountain path. These conditions cause the liquid to boil. Heat destroys chemical structures. You can see that the change feels harsh. Or boring. Both are symptoms of ATF deterioration.
The manufacturer recommends replacement every 20,000 to 25,000 miles (32,187 to 40,234 km). You can pay a shop to do it for you. Or you can save money. Especially in uncertain economic times, DIY maintenance can pay off. It’s not difficult. Some information is needed. And some tools.
“The fluid temperature rarely stays in the optimal range…At such high temperatures the ATF starts to break down.”
There are two ways to change automatic transmission fluid. The first is flush. Pump out the old fluid. More sludge can be removed. Enter the torque converter. it’s complicated. For this you need a transmission flusher. Most independent stores have this machine. Flush coolers, pipes and pumps. Probably not.
Another method is the “drain pan” method. Make it simpler. You don’t smoke anything. Just remove what’s drained. Some of the old fluid mixes with the new fluid. it doesn’t matter. Partial fluid changes significantly extend the life of your transmission. You can always perform a full flush at a later high maintenance interval.
Tools needed at work
You need a transmission filter repair kit. Also includes filters. The pan gasket is also new. We also need a catcher. 3-6 quarts (3-6 liters) of ATF. All gear oils are different. Don’t guess. Check your owner’s manual.
Most domestic cars use Dexron III or Melcon. This is a general rule. There are exceptions. Most pre-1992 Fords require an F-type. Toyota also uses the same F-type. If you use the wrong fluid, there is a risk of damage.
Collect the remaining equipment. Your garage can have:
- socket wrench
- driver
- mallet
- Long neck funnel
- 2 old milk jugs
- crane racks or a car ramp
- wheel chocks
- brake cleaner
- a clean rag
Measure with a milk jug. Didn’t recover. Let’s say you want to know how much volume gravity pulls out of a liquid. That gives a rough number. When you add new liquid, you know how much to pour. Do not overfill. Do not underfill.
This article explains the drain method. It causes some changes. Don’t worry about it. This works well. Manual transmission requires different steps. See these instructions for use. Or find a mechanic.
Task preparation
Before loosening the bolts, you need to do some preparations. Safety first. The car must remain stable.
I checked the dipstick. I have confirmed that the fluid level is low or dirty. Now you really need to change it. But before you start loosening the bolts, remember that new cars make DIY a pain. they hide things. They block access. If your car is newer, you may face some struggles.
Locate the oil pan and drain the ATF.
First, locate the oil pan. This is the automatic transmission fluid (ATF) reservoir and is located just below the dipstick tube you are using. On some models you need to remove the oil pan first. In some cases, the transmission system can also be in the way. Remove those barriers.
When you see the pan, check if it has a drain plug. If you’re lucky, find it and unscrew it. Otherwise, the whole thing will burn out.
Do not remove all bolts at once. I’m sure you’ll regret it.
Place the large collection container down. Loosen the bolts securing the pan to the gear case. Stop before the fluid runs out. Leave a few bolts on the other side. Use a rubber mallet to tap the corner of the pan to remove the gasket. Tilt the pan away from you. Turn the remaining bolt and most of the old fluid will drain into the collection container.
When the fluid starts to run down, remove the remaining bolts and lift the pan. Pour the remaining fluid in the pan into the collection container.
You need to know approximately how much fluid will come out. Transfer the drained ATF to an empty 1 gallon milk jug. Exact measurements are not required. Know how much to replace.
Next, remove the old transmission filter. It is attached with bolts or clamps and sometimes sealed with an O-ring. If it’s sealed, twist and pull. Please throw it away. It did its job. It’s already rubbish.
Cleaning and reassembly
My old filter is gone. The fluid came out. Now you need to deal with the dirty pan.
Scrape off the old gasket material. Clean the pan surface with brake cleaner or degreaser. If any debris remains, it will mix with the new fluid and cause problems later. Check the pan for cracks or damage. If bent, replace.
Install a new filter. Before installation, make sure the O-ring is lubricated with fresh ATF. This prevents tearing during installation.
If your pan uses this method, apply a new gasket or RTV silicone. Don’t use too much. All you need is thin, uniform beads.
Return the pan to the transmission. First, tighten the bolts by hand. Then tighten with a torque wrench according to the manufacturer’s instructions. If you tighten it too much, the pan may crack. Leakage due to insufficient tightening. Find a middle ground.
Filling fluids and checking levels
Most people fail here.
You need to add a new ATF. But it’s not just about filling it up. Transmission systems have internal volume limits. We want to put back what came out of the transmission and what’s in the torque converter and radiator lines.
See owner’s manual. It will tell you the capacity. I usually add about 2-3 liters at first. Then start the engine.
Change all gears. Leave it alone. Check the dipstick. Add fluid as needed. The fluid should be pink and smell clean. It’s not brown. Didn’t burn.
If the fluid looks black or smells like burnt rubber, the problem is bigger. Changing the fluid alone will not fix internal wear. Leave it to the experts.
But what if everything looks fine? You’re done. Or so I think.
Drive for a few days. Check the level again. As air leaves the system, the fluid level drops. Turn it off if necessary.
Then forget it. At least for the next 20,000 miles.
Final steps: preparing the seal, changing the filter, filling the liquid
Wipe the inside of the gearbox clean with a cloth before touching the new fluid. You can see the remnant. Don’t panic if metal shavings appear. If the gearbox is in good condition, a small amount of wear residue will drain into the sump. Too many particles indicate a different problem. This indicates internal damage. If your pan has a particle magnet at the bottom, clean that too. Captures ferrous debris before it circulates back into the valve body.
Then clean the gasket. Remove most of the old gasket by hand. It references a sticky residue. Use a knife or flat-head screwdriver to scrape the mating surfaces. be careful. Do not damage aluminum or steel. Brake cleaner can dissolve stubborn debris. Also spray the bolts. Corrosion can cause threads to loosen later.
Let everything dry. Install a new filter immediately. Place them precisely. The O-ring must be firmly in the groove and not twisted. Fasten with the original bolts or clamps.
Slide the pan back into place. Use the sealant specified by the manufacturer. Rubber or cork. Rubber gaskets are usually self-sealing. There is usually no cap. If using cork or non-self-sealing rubber, first apply the fixing cement.
Start each pan bolt by hand. two passes. Then tighten. Do not use excessive torque. The gasket is broken and leaking. If the torque value is not mentioned in the service manual, use “tighten with a screwdriver” as an instruction. This is enough to compress the gasket without deforming the gasket surface.
Then add the liquid. In most cars, you can pour oil through the dipstick tube. Use a long neck funnel. Pour slightly less than the total amount last used. Don’t fill it up yet.
Start the engine. Let it idle for at least a minute. Turn on the parking brake and service brake. Move the selector to each gear. park. drive. Reverse. neutral. This activates the torque converter and fills the cooling lines.
Check the dipstick. Add fluid to 8mm below the fill mark. Run the engine to normal operating temperature. Check again. The surface of the liquid must be in the hot range.
Overfilling is just as dangerous as underfilling. Aerated liquids can cause overheating and pressure spikes. Add slowly. Check back often. One wrong move can cause the clutch pack to leak or burn.
When set correctly, a hum can be heard from the gearbox. If you make a mistake, you come back to the pan with a new gasket.
Looking for more DIY tasks?
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References
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Ijavik, Jack. Automotive Technology: A Systems Approach, 4th ed. Thomson-Delmar learning. 2005.
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Freudenberg, Bob. “Saturday Mechanic: Change Transmission Fluid.” Popular Mechanics. June 2003 (October 28, 2009). http://www.popularmechanics.com/how_to_central/automotive/1272521.html
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Prudeman, Charles. “Car Repair: Do It Yourself, But Do It Right.” MSN Auto. (October 28, 2009) http://editorial.autos.msn.com/listarticle.aspx?cp-documentid=1088044
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Wakefield, Donald. “How to change the transmission fluid correctly” Automotive tips and advice. August 18, 2009. (October 28, 2009)http://autotips.plentycar.com/how-to-change-transmission-fluid-properly-part-1/
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Sklar, Deanna. Car repair for dummies. Hungry Minds, 1999.
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Yahoo! Car Care. “How often should I change my automatic transmission oil?” (October 28, 2009) http://autos.yahoo.com/maintain/repairqa/transmission/ques123_0.html
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The Unofficial DMV Guide. “Change the transmission fluid.” (28 Oct 2009) http://www.dmv.org/how-to-guides/transmission-fluid.php
