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Transmission Fluid and Filter Replacement
 
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Pelican Technical Article:

Transmission Fluid and Filter Replacement

Steve Vernon

Time:

3 hours3 hrs

Tab:

$100 to $320

Talent:

***

Tools:

36mm, 13mm socket, 6mm, 5mm Allen, E10 socket, T30 Torx, rags, bucket, fluid pump, infrared thermometer, adaptor for transmission fill

Applicable Models:

Mercedes-Benz C250 (2012-14)
Mercedes-Benz C300 (2008-14)
Mercedes-Benz C350 (2008-14)

Parts Required:

Transmission filter, gasket, new hardware, fluid, crush washers

Hot Tip:

Clean everything really well

Performance Gain:

Proper operating transmission

Complementary Modification:

Engine oil and filter

The Mercedes 722.9 transmission comes from the factory "sealed for life", yet they make a replacement transmission filter, fluid and gasket. While these transmissions where originally thought to never need service, they do, and you can do it yourself and save a lot of money. The main problem with servicing this transmission yourself is that there is no way to pour the fluid in from the top of the vehicle so you must fill the transmission from the drain plug below. While this can be messy, it can be done if you have the right tool and a fluid pump. If you don't have a proper tool to screw into the drain plug and pump the fluid up into the transmission you will not be able to accomplish this job so please to do not start it without the right tools!

You will need to safely raise and support the vehicle along with removing the transmission under tray. Please see our articles on these procedures for additional assistance.

To perform the job correctly you are going to want to drain the fluid from the both the transmission pan (red arrow) and the torque convertor (yellow arrow).
Figure 1

To perform the job correctly you are going to want to drain the fluid from the both the transmission pan (red arrow) and the torque convertor (yellow arrow).

Place a large bucket capable of holding at least six liter of fluid under the transmission and use a 6mm Allen wrench to remove the drain plug (red arrow).
Figure 2

Place a large bucket capable of holding at least six liter of fluid under the transmission and use a 6mm Allen wrench to remove the drain plug (red arrow).

Always replace the crush washer every time you remove the drain plug.
Figure 3

Always replace the crush washer every time you remove the drain plug.

There is a plastic standoff pipe inside and on top of the drain plug opening.
Figure 4

There is a plastic standoff pipe inside and on top of the drain plug opening. Once the fluid has stopped draining insert a punch or other suitable drift to pop the plastic pipe off inside the transmission (red arrow). This will cause another approximately three liters of fluid to drain out so be prepared.

Use an E10 socket and remove the six bolts and hangers (red arrows) holding the pan to the transmission.
Figure 5

Use an E10 socket and remove the six bolts and hangers (red arrows) holding the pan to the transmission. Use care as once the bolts are removed the pan is free and it will also still have a fair amount of dirty fluid in it.

Some vehicles have a bracket attached to the front right of the transmission and you will need to use a T30 Torx and remove this screw (red arrow).
Figure 6

Some vehicles have a bracket attached to the front right of the transmission and you will need to use a T30 Torx and remove this screw (red arrow).

Remove the old gasket from the pan.
Figure 7

Remove the old gasket from the pan.

Clean the old pan really well, making sure to get all of the old fluid and material removed.
Figure 8

Clean the old pan really well, making sure to get all of the old fluid and material removed. It is really important that this is cleaned well and that there is no lint, threads or any foreign matter left behind.

Install the new tube on the top of the drain plug making sure it clicks in place.
Figure 9

Install the new tube on the top of the drain plug making sure it clicks in place.

Place the new gasket on the pan making sure there is nothing interfering with the seal between the gasket and pan.
Figure 10

Place the new gasket on the pan making sure there is nothing interfering with the seal between the gasket and pan.

Pull the old filter down and out from the transmission.
Figure 11

Pull the old filter down and out from the transmission. It is held in place by an O-ring in the transmission port (red arrow). Use care as there will be additional fluid in both the transmission and filter that will escape when you remove the filter.

Install the new filter by pressing it up in place.
Figure 12

Install the new filter by pressing it up in place.

Install the pan and gasket using the old hangers but new bolts.
Figure 13

Install the pan and gasket using the old hangers but new bolts. Tighten the bolts in the pattern shown. Tighten each bolt to 4NM and then an additional 180 degrees.

Depending how your car is equipped will determine what you need to move to drain the torque convertor.
Figure 14

Depending how your car is equipped will determine what you need to move to drain the torque convertor. On our project car we needed to remove the cross bracket for the exhaust. Remove the four 13mm nuts on the bracket by the cats (yellow arrows) and then the two 13mm bolts holding the bracket to the transmission (red arrows).

Remove the bracket and the rubber plug covering the access hole to the torque convertor.
Figure 15

Remove the bracket and the rubber plug covering the access hole to the torque convertor. Use a 36mm socket and rotate the engine using the crankcase pulley until you can see the plug on the torque convertor. Place your bucket under the torque convertor and use a 5mm Allen to remove the plug and drain the fluid (red arrow). Install a new torque convertor drain plug and torque to 10NM if your plug is 8mm and 15NM is the plug is 10mm. Reinstall the exhaust bracket.

Measure the amount of fluid that you have drained from the vehicle, you are going to want to pump in approximately the same amount plus around an additional liter.
Figure 16

Measure the amount of fluid that you have drained from the vehicle, you are going to want to pump in approximately the same amount plus around an additional liter. This is where you need the proper tool that will allow you to screw into the drain plug and pump the fluid in (red arrow). I attached the tool to a power bleeder to pump the fluid in.

Since the tool I purchased did not have a shut off valve I quickly removed it and installed the drain plug.
Figure 17

Since the tool I purchased did not have a shut off valve I quickly removed it and installed the drain plug. Start the car and with your foot firmly on the brake run the vehicle through the gears. Place the car in park and allow the temperature of the pan to get to 45 degree C.

With the transmission at 45C you want to remove the drain plug or open the valve on your tool.
Figure 18

With the transmission at 45C you want to remove the drain plug or open the valve on your tool. If you have done this correctly a steady stream of fluid will come out and then once it gets to the correct level it will start to sputter out in smaller quantities. Once it starts to sputter you have the correct level and now install the drain plug and torque to 22NM. If No fluid comes out then you did not fill the transmission enough and you will need to add fluid and repeat the procedure. Install the under trays and you are done.

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Comments and Suggestions:
springer3 Comments: I am experienced with decades of MB models but cannot figure out the transmission oil and filter change on my 2014 CLA 45 AMG. It is 7 speed dual clutch automatic. Any help? Should I pioneer this procedure and report back.
August 22, 2016
  Followup from the Pelican Staff: Your model has a drain and possibly a filter at the transmission. use the drain plug on the transmission housing to drain, then replace filter. FIll at the dipstick tube, check level when warm using a dipstick, you will have to buy a dipstick. Vehicle doesn't come with one.

We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Coneman Comments: Can't tell you how blown away I am by these tutorials. Getting my list of needed items together. You've made a customer for life.
Thanks Dave
May 27, 2016
  Followup from the Pelican Staff: Glad to hear it. - Nick at Pelican Parts  

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