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Automatic Transmission Fluid and Filter Change
 
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Pelican Technical Article:

Automatic Transmission Fluid and Filter Change

Steve Vernon

Time:

3 hours3 hrs

Tab:

$200

Talent:

***

Tools:

5mm Allen socket, 27mm, 13mm socket, funnel, rags, drain pan, dipstick tool, Philips head screwdriver

Applicable Models:

Mercedes-Benz W124 (1986-95)

Parts Required:

Fluid, filter kit, dip stick or infrared thermometer

Hot Tip:

Put a drop sheet under the work area

Performance Gain:

Proper shifting transmission

Complementary Modification:

Change transmission mount

One of the less common maintenance tasks that are performed on a car is changing the transmission fluid. Typically, you'll want to change the fluid every 30,000 miles or so along with the filter in the transmission. If you are driving primarily in city traffic, you may want to consider changing the fluid every 15,000 miles. In the 1990's, there were more than a few major automobile manufacturers advertising that they had developed transmissions that required no fluid changes. The fluid inside was considered to be "lifetime" oil, meaning that it never needed to be changed. Over the years, it seems that this may have been an overly ambitious claim. We recommend that you make changing your oil and filter part of your regular maintenance.

Begin by safely jacking up and supporting your vehicle. Please see our article on safely raising and supporting your W124. Place a large trap or drip sheet under the car; have a large drain pan and lots of paper towels ready.

You will need to drain the old fluid from two locations on the transmission.
Figure 1

You will need to drain the old fluid from two locations on the transmission. In this view, looking from the rear of the car, you'll see the main drain plug (yellow arrow) near the rear of the transmission pan on the right side and the drain plug located in the torque converter (red arrow, plug not visible).

In order to access the drain plug in the torque converter, you'll need to rotate the engine until the plug is accessible through the window in bell housing.
Figure 2

In order to access the drain plug in the torque converter, you'll need to rotate the engine until the plug is accessible through the window in bell housing. The easiest way is to place a 27mm socket on the front crankshaft pulley (red arrow) and turn the motor over until the plug is visible in the window. You'll need to remove the front splash shield as well as the fan shroud. Please see our articles on these procedures for additional assistance.

With the engine rotated so that the drain plug is accessible through the lower opening use a 5mm Allen and remove the plug (red arrow).
Figure 3

With the engine rotated so that the drain plug is accessible through the lower opening use a 5mm Allen and remove the plug (red arrow).

Have a container ready to catch the fluid and so you can measure the amount that drains out.
Figure 4

Have a container ready to catch the fluid and so you can measure the amount that drains out. Also, always dispose of old fluids according to the regulations where you live. Never pour it in the street. Fluid will run and drip down the converter and bell housing and out the drain hole in the bottom of the bell housing so be prepared for it (red arrow).


Remove the 5mm Allen plug on the pan (red arrow).
Figure 5

Remove the 5mm Allen plug on the pan (red arrow). 

Again; have a container ready to catch the fluid (yellow arrow) so you can measure the amount that drains.
Figure 6

Again; have a container ready to catch the fluid (yellow arrow) so you can measure the amount that drains. The transmission has a very narrow tolerance for the level of fluid in it and it is a good idea to add as much clean new fluid when you begin refilling as you drained old fluid out.

Replace the crush washer on bolt blots and reinsert them.
Figure 7

Replace the crush washer on bolt blots and reinsert them. There is going to be fluid left in the pan when you remove it and you do not want it spilling out of an open drain plug.

Squeeze the plastic clip on the hose that runs down the left side of the transmission (red arrow) and remove it from the supporting bracket (yellow arrow).
Figure 8

Squeeze the plastic clip on the hose that runs down the left side of the transmission (red arrow) and remove it from the supporting bracket (yellow arrow). Depending on whether your transmission has been serviced before there may be additional zip ties attaching cables to the transmission; remove them if they are present.

Remove the six 13mm bolts holding the transmission pan (red arrows, three shown).
Figure 9

Remove the six 13mm bolts holding the transmission pan (red arrows, three shown). It is a good idea to leave two bolts (one in each corner) until you are ready to remove the pan. Even with draining there will be a surprising amount of fluid still in the pan. Place a hand on the pan and remove the final two bolts and then lower the pan carefully. Measure the amount of fluid in the pan.

Carefully pour the fluid into your catch container and inspect the pan for any metal shavings or pieces.
Figure 10

Carefully pour the fluid into your catch container and inspect the pan for any metal shavings or pieces. A small amount of micro shavings can be normal; you should not find any pieces or metal build up in the pan (red arrow). Carefully clean the pan with a lint free cloth.

The thick rubber gasket hooks onto the pan on both sides.
Figure 11

The thick rubber gasket hooks onto the pan on both sides. Carefully lift up on the hooks to remove the old gasket and clip the new ones in place when installing the new gasket (red arrow).

Remove the three Philips heads screws that hold the filter in place (red arrows).
Figure 12

Remove the three Philips heads screws that hold the filter in place (red arrows). The filter will be full of fluid so use care when removing it.

Remove the old filter form the transmission and inspect it for any metal.
Figure 13

Remove the old filter form the transmission and inspect it for any metal.

The new filter will have two gaskets where it meets the transmission.
Figure 14

The new filter will have two gaskets where it meets the transmission. Make sure to remove the old gaskets from their ports (red arrows) before installing the new filter.

Locate the automatic transmission filler hole near the firewall on the passenger side of the engine.
Figure 15

Locate the automatic transmission filler hole near the firewall on the passenger side of the engine. You'll notice a plug in the top of the tube that reads "MB Workshop Only". You'll need to remove this plug to continue. You can just barely move the red release lever inside the plug with a small screwdriver (green arrow). Once the release is free, just pull the plug up and out of the tube.

Now fill the transmission with 5 quarts of Mercedes-Benz branded transmission fluid; it is critical that you use the original MBZ fluid in this application.
Figure 16

Now fill the transmission with 5 quarts of Mercedes-Benz branded transmission fluid; it is critical that you use the original MBZ fluid in this application. Safely run the car through all the gears to circulate the fluid through the transmission.

Check the dipstick tool for the transmission.
Figure 17

Check the dipstick tool for the transmission. You will see two gradients on it. One level shows the transmission level at 25 degrees C, and the other at 80 degrees C. The idea here is that you want to check the level of the fluid at two different temperatures. As the temperature of the fluid increases, the level of the fluid will rise. The 25 degree mark (green arrow) is supposed to indicate a cold fluid level while the 80 degree mark (purple arrow) is with the transmission fully warmed up.

Now start the car with the wheels off the ground and run it at idle through reverse, drive and all other gears for 30 seconds each to circulate the fluid already in the transmission.
Figure 18

Now start the car with the wheels off the ground and run it at idle through reverse, drive and all other gears for 30 seconds each to circulate the fluid already in the transmission. With the engine still running, place the dipstick tool into the tube and push it in as far as it will go. Keep in mind that it will not go all the way down to the handle.

You will need to monitor the temperature of the fluid as the car warms up.
Figure 19

You will need to monitor the temperature of the fluid as the car warms up. For this task, an infrared pyrometer is an invaluable tool. This tool allows you to point a laser beam at any given object and see the temperature. In this case, you would want to set the tool to Celsius and point it at the transmission pan until it reads roughly 80 degrees C (this will take a while). At this point, pull the dipstick out and read the level. If the level is correct, it will read between the lines for the 80 degree gradient on the dipstick. If it does not register, add more fluid until it does. You'll need to have the engine running and the transmission in park as you do this. Keep in mind that you will need to circulate the fluid between each time you fill by running the transmission through the gears. Once done, put the car back in park and re-check the level. It's a time consuming process, and you want to make sure that you get it just right. The fluid level MUST be correct or you could cause damage to the transmission.

This photo illustrates what the dipstick tool should look like at the correct fluid level at 80 degrees Celsius (green arrow).
Figure 20

This photo illustrates what the dipstick tool should look like at the correct fluid level at 80 degrees Celsius (green arrow). As you can see here, the fluid level comes up and over both sets of marks on the tool, indicating that the fluid level is correct. You want to aim for in-between the marks on the upper, 80 degree gradient. In this picture, we are just a tad on the high side.

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Comments and Suggestions:
matt Comments: My 1987 300e has transmission dipstick that has is different from the one in the article. what's up ..the marks are different.
August 5, 2016
  Followup from the Pelican Staff: It is a different style, can you share a photo? Checking the level should be similar. - Nick at Pelican Parts  
max Comments: Thanks for replies! I'll be probably ordering a flex plate next!
July 6, 2016
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it.
- Nick at Pelican Parts
 
Max Comments: You said to "run it through all the gears" with the wheels off the ground.
I assume you mean the rear wheels and I'm letting it spin up to shift into 4th gear?
Sounds potentially dangerous to assume so I thought I'd ask "the dumb question" just to be sure.
July 1, 2016
  Followup from the Pelican Staff: Vehicle has to be lever when checking fluid level, so all four off the ground. Running the vehicle on jack stands or a hoist is normal practice, only unsafe if your lifting practices are unsafe. Up to the user to ensure personal safety and a securely lifted vehicle. - Nick at Pelican Parts  
Max Comments: You noted that there are two gaskets on the filter that should be removed from the ports ... my new filter has two cork gaskets already on it ... DO I NEED TO PURCHASE ADDITIONAL GASKETS OR ARE THOSE CORK GASKETS ALREADY ON THE NEW FILTER WHAT YOU ARE REFERRING TO?
July 1, 2016
  Followup from the Pelican Staff: Where did you buy the gasket kit from? Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
max Comments: I just checked with my local MB dealer when I was buying the washer for the 5mm drain plug and the parts guy looked it up and confirmed that FOR THE 1987 124 model wagon, regular Dextron III was acceptable ... so QUESTION: TO YOUR KNOWLEDGE WHY IS IT IMPORTANT TO USE THE MBZ TRANNY FLUID? WHAT ID THE DIFFERENCE?
perhaps Dextron III is only good for my particular model and not others? Just curious, not trying to be a troll. Just trying to understand these things.
July 1, 2016
  Followup from the Pelican Staff: benz fluid is made specifically for the trans. Including any additives or friction modifiers. I can't argue with Mercedes. if you got advice from them, follow it. - Nick at Pelican Parts  
jesse Comments: I just bought a transmission filter kit for a 1993 Mercedes 300e 2.8 and came with the filter, pan gasket, and three washers. 2 larger washer and a smaller one i know the 2 larger washer would go on the drain plugs but any idea what the smaller washer goes to?
January 21, 2016
  Followup from the Pelican Staff: It may be for a different model the filter kit also fits. - Nick at Pelican Parts  
Andrew Coulter Comments: Wayne, The first paragraph of this article is very wrong, talking about 80,000 miles between ATF changes.

My 1987 Mercedes 300E factory maintenance manual specifies ATF changes every 30,000 miles, unless it has severe service, such as city traffic driving, where 15,000 miles intervals are recommended.

My 1999 Porsche manual recommends ATF changes every 100,000 miles, which if you do that, has the tiptronic shifting very poorly, so I change the fluid every 50,000 miles.

I have checked with guys who drive pickup trucks under severe conditions and they all say that to avoid transmission difficulties, they change the ATF every year.

So, you are right, transmissions are neglected, and the solution is to change the fluid quite often.

Best Regards,
Andrew
January 18, 2015
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.


I will have someone look into updating the article

Generally, 100k fluid is lifetime fluid, meaning the lifetime of the transmission. Which most parts have a lifetime of a 100k. This reduces assumed service costs, when relayed to the consumer for purchasing new vehicles. - Nick at Pelican Parts
 

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