If you're like me, you've probably found this thread because you like working on cars. That, or you've found this thread because your cheap like me and don't want to pay a dealer, especially a Mercedes dealer, for a fairly simply fluid change. In any case, I thought I would share this for anyone looking to perform this service on their own because I could not find a thread anywhere for the newer W463s. There are some good videos on youtube and some threads on some of the MB forums on how to perform service on the 722.9 transmission, and those same steps apply on the G63 but there are a couple little nuances that you need to consider. I'll outline how to change and flush the transmission. For those who have not completed these services on a vehicle before, it's NOT the same thing. A change is just dropping the pan and replacing the fluid. A flush includes the fluid that is in your powertrain, I.E the fluid lines and the torque converter.

Long story short, change your transmission fluid but a flush is even better. This counsel isn't just targeted on a G63, and includes any vehicle even outside of Mercedes. Even if you choose to pay a dealer, change your fluid. For anyone here who is mechanically inclined and understands how important this is, I want to echo your concerns to the people reading this who don't think transmission fluid changes/flushes are a big deal. This is a big deal. I've argued that outside of a standard oil change, changing your transmission fluid is the single most important fluid change on your vehicle that produces drastic results. As long as you complete the process correctly, you will feel the difference the first time your vehicle changes gears after you start your car. I'd classify this as the "need to do it or potentially look at a huge repair bill". This would be in the same class as a motor going to **** because you didn't change the oil.

My vehicle is a 2016 G63 but I wouldn't doubt this would apply to the entire 2012-2018 model years inclusive of the G550. Per the service manual, a five year transmission fluid change is standard but after completing this service, I'll be completing this every three years on any Mercedes I own in the future. FWIW, this model year G class utilizes the updated 722.9 transmission pan and blue ATF FE fluid.

The problem
About a year ago, my transmission started to shift a bit rougher than normal. Not bad compared to other vehicles, but I thought this was expected since the G63 is a heavy duty SUV. A few weeks ago, I noticed gear shifts from first to second, and second to third were slipping worse than normal. All of the other gear changes including down shifts were a bit rough but not as bad as gears 1-3.

For those who don't know what slipping feels like in an automatic transmission, it's when your gear shift is delayed. It's that feeling you have when the gear shift initiates, but there is that split second prolonged lag before it goes into the next gear and usually bangs into gear with a slight shutter.

After the fluid change, it was like driving a new car. Shifts were seamless and you couldn't feel the car vibrate through the chassis on any shifts. 1-2-3 gear shift slips were gone. Downshifts cleared up as well and were very precise compared to this morning before I changed the fluid.

Now the good stuff:

• Expected Time: 3 hours for a change, 4 hours for a flush. Cut that time in half if you have a lift, preferably a 2 post lift.
• Difficulty: 2 out of 10 for the change. 3 out of 10 if you flush because there are some fluid lines you will need to remove.
• Parts: FCP Euro Carries a complete transmission fluid flush kit for around $150 or so. If you complete a change, you'll just use 5 liters of fluid vs the 10 they give you. If you really want to save money, use their part list and buy the parts on your own. You will also need a 722.9 fill adapter, which FCP carries as well.
• Tools: Outside of standard hand tools and the stuff you see on youtube, I would highly recommend an infrared thermometer. The final procedure to level check the fluid requires a device plugged into the diagnostic port to monitor the transmission fluid temp. In lieu of this, I used an infrared thermometer to measure when the pan got to 114 degrees farenheit.

And now for the instructions. I am going to generalize here because you can find the standard procedures on the 722.9 transmission on youtube, and the process is spot on. The longer explanations below are the things I learned specific to the G63.

Transmission Fluid Change

1. Drive around and warm up the vehicle. It makes draining the fluid easier.
2. Go under the vehicle, and remove the drain plug from the pan and allow fluid to drain. Stick a screwdriver in the hole and push the plastic overfill pipe out.
3. As this drains, remove the 6 torx screws from the transmission cover. four corners first, then two in the middle. Be careful and tilt the pan slowly because there is still a lot of fluid in the pan.
   1. G63 Specific: I think this is unique to the G class but you need to remove the 2 push fasteners holding a sensor line from the front bumper side of the pan. There is also a metal clip on the driver side holding that same line to the pan. Be careful with these. If you're not sure which line it is, it will be obvious because you can't remove the pan without taking these clips off.
4. Remove the old filter after you remove the pan.
5. Clean off the magnet, and the pan. Reattach the magnet. Install new fill pipe, rubber gasket and copper washer on to the drain plug. Set the drain plug aside.
6. Install the new filter into the valve body. Install the pan and with the new pan bolts, torque down. Spec calls for 4 nm + 180 degrees, but I tightened these to the weight I felt when I broke the bolts loose. 4NM coverts to about 3 ft pounds so be careful because that is not a lot of torque. If you don't have a torque wrench that goes to 3 foot pounds, get a feel for much torque there was when you broke the bolts loose, and it will be pretty easy.
7. Reinstall clips from sensor line
8. Install fill adapter onto a pump. This can be a hand pump or whatever fill pump you'd like. Fill 5 liters of fluid into the pan. The FCP euro kit includes Pentosin blue 134 FE, but any fluid off the MB 236.15 spec will work.
   1. If you wish to flush your vehicle, stop here and go to the steps below
9. Start the car while the fill pump is still installed. Wait for the pan to hit 114 degrees F using a thermometer or your diagnostic device.
10. Shut off the car. Get your drain plug. Remove the fill adapter, and fluid should start to rush out. Once this goes to slow drip like stream, install your drain plug and you're done.
    1. If no fluid comes out, add more fluid, and repeat step 9

Transmission Fluid Flush

1. Spec calls to rotate the crank, but it's much easier to remove the transmission fluid return line. Pick whichever you prefer.
2. Find the torx head holding the return line that goes into the transmission. This is located on the passenger side just above the front bumper side of the pan. Can't miss it because it's a metal line going into the transmission.
   1. G63 specific: Before you remove the line, there are two other torx bolts you need to remove. Follow the return line around to the driver side and you can easily spot these two bolts. One is on the driver side of the line fitted to a clamp holding two fluid lines. The other is on a small bracket that bolts to the transmission. You cannot miss these and it will be obvious once you follow the fluid line.
3. Pull out the return line going into the transmission. Since you removed the other two torx bolts, this will fall freely and will drip fluid so get a pan to collect the fluid.
4. With a 1/2 inch rubber tube like you would find on a hand pump, attach that onto the return line, then put the other end into an empty container that is easy to measure. I just used one of the empty pentosin jugs because there is a fluid level indicator..
5. Starting here, pay attention to what you are doing.
6. Turn the vehicle on. Hydraulic pressure will push the old fluid out and recycle with new fluid. The idea is the same as a brake bleed, but the fluid comes out very fast. Easily 1L every 5 seconds. Once 1-1.5 fills, shut the car off.
7. Pump in fresh fluid, It is very important to be aware that even when the vehicle is off, there is still pressure in the line so fluid will slowly continue to drip out into your used container. Pay attention to how much fluid has come out.
8. Dependent on how much fluid has come out, turn the car on, and fill the dirty container to about 4L or to when you see the transmission fluid turn blue again.
9. Shut the car off. remove hose from return line, and reinstall into the car to stop fluid from coming out the vehicle. Reattach torx bolts and torque down.
10. Continue to pump fluid until your second jug of pentosin empties. You now have 10 Liters of new fluid in the vehicle, five from your pan change, and five from line/torque convert flush.
11. Start the car while the fill pump is still installed. Wait for the pan to hit 114 degrees F using a thermometer or your diagnostic device.
12. Shut off the car. Get your drain plug. Remove the fill adapter, and fluid should start to rush out. Once this goes to slow drip like stream, install your drain plug and you're done.

I hope this helps. My vehicle drives like a new car again and is a night and day different, and I hope yours does as well.

 

Wow wow wow. You my friend deserve an award

this is the most detailed post I’ve seen on here. If not one of them. I def will be changing my transmission fluid soon and I def will be showing this post to my Indy mechanic. Few questions:

1: Did you do a change or a flush?
2: how many miles does your car have?

 

Thanks for a most detailed procedure - much better than what we'd find in a shop manual, if such existed. I'm yet a long way from doing this on my 2019 G550, but this post and a couple preceding it reminded me that my vintage Wrangler is due a complete transfusion -- tranny, xfer case, & both diffs. Total cost for fluids & gaskets -- $100 @ Napa. And everything, even for a 25 year old Jeep, is in stock in a rural Colorado store.
Gonna print out your post and put it in my maintenance notes file. I really enjoy these kinds of forum posts -- a pleasant change from others asking for help in deciding what color paint to order.

 

a flush. The minor amount of incremental work to flush this vehicle was worth the extra hour of time. The only problem with changing just the pan is you’re mixing your five liters of fresh fluid with five liters of dirty fluid.

I have 40,700~. A year ago, I had right around 34,000.

no problem

 

This guide is extremely helpful and I used it to do a 722.9 service. However, one step that I wanted to call attention to - The Mercedes WIS (as well as FCP's DIY video) says to remove the fill adapter and check if fluid comes out WHILE THE ENGINE IS ON AND CAR IS IDLING as opposed to when the car is shut off.

 

Such a great post thx !!

 

Good catch. Exactly how I did it on my c300...engine running.

Now I need to tackle the fluid on the G