ATF fluid removal and replacement on VW TDI engines

Difficulty: 2/5
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Introduction

Unlike a manual transmission, you can't just drain the fluid and add the suggested amount back.  You should warm up the car a little, drain, refill, and then top it off with the engine running and ATF at a certain temperature range.  Suggested change intervals are every 80,000 miles or as needed, depending on use and personal preference.  Unlike the manual transmission, OEM fluids are highly recommended for the automatic transmission.  

If you go to the dealership, they may tell you that VW/Audis have lifetime fluid and is not serviceable.  What they mean is that when the fluid breaks down and the transmission breaks, it ends the economically useful lifetime of your car, so come back and buy a new car.  Lifetime might also mean the lifetime of your car's warranty.  There is no such thing as fluid that has an infinite life.   In theory, the lifetime fluid itself could last a very long time without issue.  The problem is that it gets contaminated with water or fine particles, faulty auto transmission filters, or leaks/seeps out.

You may hear that if a high mileage car (well over 100,000 miles) has never had the ATF changed then you shouldn't change it because the new fluid will cause leaks or slipping.  The reason why this sometimes happens (usually doesn't) is because residue built up on the gaskets and seals is preventing external and internal seepage and leaks.  The dirty fluid also provides some internal friction which prevents slipping. The fresh detergents in the new fluid cleans the residue out.  On the other hand, not changing the fluid could also cause future problems.  While the best thing is to regularly change the fluid, I suggest changing it even on high mileage cars because not changing it will result in more problems. Draining/refilling the old fluid also doesn't change all of the fluid because some will be left in the torque converter and sitting in the corners. Using an ATF flushing machine will change all the fluid and may increase the chance of having problems.

In a manual transmission, the differential and transmission share gear oil.  In an automatic transmission, the differential and transmission are separate and use different fluids.

Parts and tools

FOR TRANSMISSION ONLY: 
5.3 liters/5.6 quarts total capacity (I would suggest getting a little more because some will spill) 
VW# g052 162 a2 (or a1) full synthetic ATF transmission fluid or 1 liter pentosion equivalent VW TL52162 spec ATF fluid or Febi brand ATF
Replacement fill plug  (01M 321 435 B and 01M 321 432 A) 
screwdriver  
ATF filter VW# 01m 325 429

transmission

FOR DIFFERENTIAL ONLY: 
.75 liters/0.8 quarts 75w90 VW# g 052 045 a1 (or a2) synthetic gear oil g 052 162 a2

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Procedure

First start the engine and warm it up until the transmission pan is luke warm.  The procedure in the factory service manual specifies a test temperature of  95oF-113oF.  Use a Ross tech VCDS cable to measure the ATF temperature.  Shut the engine off before that temperature is reached so that it's at the test temperature later when you refill.  

Engage the parking brake, jack up the car using the factory jack points, rest car securely on jack stands, and make sure the car is safe and secure before doing anything else.  The car must be level, otherwise the fluid level will not be accurate.  I use wheel blocks in addition to jack stands to raise the car as shown in 1000q: wood blocks.  Disclaimer - these are not a substitute for jack stands on the factory jack points.

Draining the fluid

Check the temperature of the transmission pan.  If it's not warm enough, run the engine in neutral or park until it is warm enough.  Once it is warm enough, shut off the car. The specified test fluid temperature is 95oF-113oF.  

Remove the transmission plug and overflow pipe.  Make sure you are not removing the engine oil drain plug!  The engine oil drain plug will be attached to the bottom of the engine and the oil pan.  See 1000q: engine oil change to see what the oil drain plug looks like!

Let it drain out and remove the red drain hole insert.  If you don't think the drain pan will catch all the fluid, put a piece of cardboard under it to act like a placemat.  This will prevent ATF fluid stains on the driveway.  This should have removed most of the fluid - some will still be in the torque converter, etc.  Replace the red drain hole insert and begin to replace the ATF.  Open the fill hole with a screwdriver.  It will probably be damaged when you remove it, so make sure you bought a replacement, part number is listed above.  Here is a cutaway drawing.  3 and 4 are the fill hole cap.  1 is the drain hole and 2 is the red drain hole insert.  

When you are replacing the fluid, first add more than 3 liters of fluid, then start the car.  Move the shifter through all the selectors, park, neutral, 4th gear, 3rd gear, etc..  Leave the engine running and keep adding fluid until it flows out of the level fill hole, marked with "2" in the picture above.  Do not shut the engine off or else ATF fluid will come out of the coolers and pumps and come pouring out the fill hole "2".  Clean the drain plug and then put it back while the engine is running.  Once it's back you can shut off the engine.

Refilling the automatic transmission fluid

WARNING: the engine must be running to top off the fluid.  While the engine is running, take care to keep all hands/tools/persons away from the moving belts or fans at the front of the engine and away from the hot exhaust if under the car!  Moving belts could easily rip off your hand or fingers if they get caught by the belts or fan!  If you do not have adequate clearance under the car to comfortably stay away from the belts at the front of the engine, do not attempt this job!  See the TOS Agreement for the full legal disclaimer.

There are a few ways to get the fluid back in.  You can use a gravity pump (siphon) or funnel, where the bottle is higher than the fill hole and connected with a hose.  This can be used in your VW TDI because there is adequate clearance but can't be used in many other cars.  This method with a funnel and hose is the best because it wastes the least fluid.  You can also use a hand pump designed to force fluid out of a container.  I use compressed air to force the fluid into the fill hole when there is no clearance for the funnel/hose method.

To use the compressed air method of adding fluid, first regulate your compressed air pressure down to a reasonable amount, just enough to get the fluid flowing.  If you use excess pressure, the bottle of fluid could pop so start low and then increase the pressure if the fluid isn't moving fast enough.

Poke a smooth round hole in the cap for the fill hose and at the top of the bottle for input air -smaller is better for a tight air seal, marked by the green arrow in the below picture.  I use a thin plier and rotate it to have a small tight hole without sending shavings into the bottle.  A screwdriver could work too. Now stick the hose into the cap and put the other end into the fill hole.

Use at least 1/4 diameter hose or else the fluid will have a very hard time flowing through it.  The dashed line shows the hose inside the bottle.  If the hose end is in the air, the fluid will foam.  If the compressed air hole is below the fluid level, obviously the fluid will leak out.  Too much foam will cause underfilling due to air.  If this happens, let it settle down and overfill it very slightly.  The hose has a coat hanger in it bent into an s-shape (so it stays in place) with a 90o hook at the end so I could it for various manual and automatic transmissions and to minimize dripping at the end of the hose.

Now press the compressed air nozzle into the hole in the top of the bottle marked with the green arrow in the picture above.  Warning!  Do this step last because you may accidentally press the trigger on the compressed air nozzle before the hose is in the fill hole.  If this happens, your expensive fluid is now all over the ground.  Apply gradually increasing amounts of pressure until the fluid is gone.  If the bottle stretches a little that is okay.  If you think it's going to pop, stop applying pressure.  I put my gloved hands around the bottle cap and nozzle to prevent any fluid from hitting me in case the bottle cap blows off although it hasn't happened yet.  As always, wear protective safety goggles.  Below is a picture of it in use on different style of transmission.  It's pictured here as a tip that you can use on other cars.

When you go to the next bottle, just move the cap to the next bottle and poke another air intake hole in the next bottle.  Don't let the hose touch the ground because it will get dirty.  If it gets dirty just thoroughly wipe it off.

Like this tip?  There are many more tips for the mechanic at 1000q: mechanics tips.

After you're done, hang the hose with a paper towel or two on the end and let it drip dry.

If you spilled some ATF fluid on the ground, first wipe it up with paper towels.  Then pour some kitty litter or driveway spill absorber and step on it to grind it into the stain.  Let it sit for a while and then sweep up the gravel/dust. 


Differential gear oil

You can change this at your convenience since the fluid is separate from the ATF.  Drive around to warm up the gear oil. 

Remove the speedometer gear sensor on top of the differential.  Unplug the plug and unscrew the sensor.  It's a big black plug sticking down.  The tip has a step which is the max/min mark.  It should be between the step and the bottom of the speedometer gear.

To get the old gear oil out, suck it out through the speedometer gear sensor hole.  A hand vacuum pump like a mity-vac will work.  To refill, pour in the new fluid through the hole.  Don't overfill the differential gear oil.  The car must be level for the speedometer gear/dipstick to be accurate.

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