sak335

I just did this job on my 2012 GL350 with 80,000 miles (~129000km) and the fluid was suprisingly dirty given that it had been changed at 40,000 miles as well. It's not a difficult job, just a bit dirty. I can't imagine going through the trouble of changing the fluid and filter and NOT draining the torque converter. It takes about five minutes to rotate the crank to find the drain plug. Admittedly, it does take quite a long time for the fluid to drain from the TC because it's spilling out of that tiny hole, but go drink a beer or something while it's draining. I got the fluid off eBay (Febi/Bilstein, from Germany - I couldn't find it anywhere locally) for like 100 Euros and the rest of the parts I had bought in the US before I moved for cheap. The one thing that I keep forgetting when I do this job is that you're supposed to replace the copper crush ring on the torque converter plug and it's a very small size. So remember to order one before you do the job as it didn't come in the 'kit' that I ordered and I didn't have one that size in my stash. Also, to remove that TC plug, you need a long 4mm hex (I use a long handle T-allen wrench for this application since you can't fit an allen socket in there.)

chassis

@sak335 Thanks for the writeup. Which transmission do you have? Was the torque converter drain plug easily accessible? I have seen a video of a 722.9 fluid replacement where a small hole needed to be drilled into the transmission cast housing to access the TC drain screw. Was this your experience?

sak335

I have the 722.9 transmission that uses the 134FE (i.e. blue) fluid. When you get under the vehicle, and look at the front of the transmission bellhousing, you will see a small rubber plug, oval in shape. If you don't know where to look, it's just behind the anti-roll bar in the middle of the car. It's about the size of an egg. You grab the edge of that rubber plug with a flat bladed screw driver and gently pry it out; it will come out easily. Once you have the rubber plug out of the way you will see the torque converter up inside there. The TC is a big, hollow, metal donut. If you don't see the plug, you put a 24 mm (I think that's right) socket on the crankshaft nut and turn it with a breaker bar. You literally only turn it maybe a few inches of movement at a time. If you don't have a helper, this gets annoying, because you have to keep crawling under the car to check, but eventually you will see the bolt on the TC. The bolt is a 4 mm allen head socket and there is a copper crush washer under the head. It has thread locking compound (i.e. Loctite) on it, so it takes a bit of force to remove it, but be VERY careful not to strip the allen head. You're supposed to use a new bolt when you put it back together but I just clean the old one with brake cleaner and put a dab of loctite blue on it.

I took a photo of the tool that I use to remove this bolt:


You need the long end because the anti-roll bar gets in the way, and if you try to use an Allen socket it will be blocked by the small gap between the bar and the bellhousing cut out.

chassis

@sak335 Thanks for the clear description and the photo.

Kropf

On my 2007 GL450, it is a 27mm socket. And a 12 pt socket is a bit easier to engage than a 6 pt socket, and doesn't need much force to turn Clockwise (as looking from the front).

vesiadog

I have done many changes on 722.9’s. IMO the magnets in the pan are going to tell you the story. I use to use Shell ATF but once I switched over to Amsoil my fluids between changes starting looking like new.
I would never do a partial if the TC can be drained. If you really want to drain even more drop the valve body and inspect all the O-rings on the shift spools..8 of them . When I am pulling my bird dog trailer a lot I change my fluid 25k… if the fluid on a used vehicle is really bad I will change it again at 10k and keep changing it until I get a cleaner look.
Everyone knows that heat is the killer of tranny fluid… that’s why trucks that pull horse trailers etc always buy larger than standard tranny oil coolers , deeper pans etc. I did all of that with my 7.3 power stroke Fords while pulling horse trailers around the country and never lost a tranny.
Fluids are the cheapest cost to maintain a vehicle … and premium filters .. don’t save pennie’s on a filter .
Notice on the link that Eric supplied for the rebuilt trannys… They note Change Filter and Fluid at 24k.
I have done a lot of tranny fluid changes on both 5 speeds and 7 speeds and it is very surprising between brands of fluids on how clean some are between 20-30 k miles and some are aweful. Not all are created equal even if they meet the same spec … heat kills!

Elbeau

A service manager at my local dealer strongly recommended NOT to do a flush.I think a dealer recommending against doing a relatively east service at an exorbitant price, when requested by the customer, certainly says something.

Max Blast

Regular fluid and filter changes every 40K, no need to do anything more than that.
235 ish k on original trans here with no record of changes between 120-160k.

vesiadog

Each car is definitely unique with different situations .. If someone was hauling or gotten into a higher heat situation and the fluid was in bad shape … I would highly recommend a follow up fluid change well within 40k more like 24k.
Example I bought a used 06 ML500 around 75/80 k miles and the fluid was never changed it was horrible and it took me 3 complete changes at 20k with the last one at 10k before I got a decent looking fluid with draining the TC every time also.
When you are doing the changes yourself it is not that expensive… of course these are my experiences from maintaining 5 different MB SUV’s and a handful of 5 speed cars.
On a slightly different note my son runs a R129 parts business and he has bought well over 60 R129’s .. SL500,300’s and 320’s… guess what over half of the cars had??? blown trannys. Yep lifetime fluids 😂

01blackhawk

I have done the fluid change with torque convertor drain back in October and has lots of pictures, I can post them here upon request.
The most important part having a scanner to tell the fluid temperature, rest is just wrenching, nothing complicated.

Elbeau

Dealers don't resist suggesting extra work - especially when it's something not very complicated and the actual labor time is usually far less than the "book."
And, no, they don't resist because they hope that in a 100,000 miles or so, you will be asking them the replace the transmission. Any dealer knows current work in not turned down in favor of some vague hope a customer may return some time in the potentially distant future.

The reason they resist a full flush is well-covered in the above posts and elsewhere.

01blackhawk

I decided to put some pics here from my last change back in October at 125K miles.

I believe it was 27mm to turn the engine clockwise, I used the handle of my smaller jack to have more leverage.

I have a cheap set of long torx bits from harbor Freight to get the drain plug out, comes out just about 2 liters of atf from TC

Pan was pretty good shape, no metal shavings or anything like that just usual dust, same for the magnets. Also broke the filter and checked, same.

I let it drain overnight and filled it next day.

I used a cheap battery operated suction pump from Harbor Freight again

Got my hands on a good deal of fluid from a closing business so I jumped on those 12 jugs of Fuchs ATF

Even put a little control valve(found in the garage from a bathroom remodel project lol) on the hose when pumping the fluid to have more controlled flow especially when draining the excess fluid., used gravity`s help by locating the jug on a bar stool, so pump wouldn`t run too hard lol.

Old atf to my surprise had a goldish color you can see in the pics, dripped some on the paper towel so I can see the color better.

I drained about 6 liters from the pan, including filter and about 2 liters from TC, total 8

I filled back 8.4 almost 8.5 and started the engine, observed the temperature and once I reached 44C, I closed the valve.

Car always shifted good, did not notice a huge improvement but the piece of mind is priceless.

Hope this helps to someone thinking about doing it at home.