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2007 SLK350 6 speed manual transmission and differential oil change


I couldn't find anything definitive after searching this topic so I hope the following will be helpful:


Preparation:
1. You'll need a set of hex drain plug keys, plenty of cloths for spills and a means to get the oil into the transmission and diff. I used a length of clean hose pipe and a 1 litre oil bottle with a narrow neck to insert into the hose. There are low cost 12v oil pumps for under £20 that would be better. You'll need an oil drain pan.
2. Raise the car safely and ensure it is level. I used a trolley jack and 4 axel stands. Safety first. Ensure the car is securely supported!!


Transmission:
1. Using a hex drain plug key, loosen the transmission fill plug. This is about 1/2 way up the r/h side of the transmission housing.
2. Place an oil drain pan under the transmission. Using a hex drain plug key (larger than the one for the fill plug) remove the drain plug in the bottom of the transmission. Wait a few minutes for the oil to drain. At 48k miles, the oil was quite brown. There will be some metal flakes stuck to the magnet in the drain plug. This is normal (as long a they are just small flakes). Clean the plug with a clean cloth.
3. Remove the fill plug.
4. Replace the drain plug. Tapered plug, do not over tighten.
5. Fill the transmission with 1.5 litres (around 1.6 US Qts) with a good quality synthetic 75W/80 GL4 manual transmission oil. I used Redline MTL (see note at bottom. OP used Castrol Syntrans V-FE 75W-80 in the end) . DO NOT fill until oil is level with the fill plug. This will equate to ~2.1 litres which is far too much oil. Mercedes specifies 1.5 litres. Too much oil or a 75W/90 weight oil will reduce the ability of the synchro rings to do their job resulting in stiffer or more notchy gear shifts.
6. Replace the fill plug again taking care not to over tighten.



Differential:
1. Using a hex drain plug key, loosen the fill plug on the l/h side of the diff housing.
2. Place an oil drain pan under the diff.
3. Using a hex drain plug key, remove the drain plug on the bottom of the diff. Wait a few minutes for the oil to drain. Again, on my car the oil was fairly dirty.
4. Remove the filler plug and refit the drain plug. Do not over tighten.
5. Fill the differential with a good quality synthetic 75W/90 GL5 gear oil. I used Redline 75W/90 GL5. Fill until the oil is level with the bottom of the fill plug hole (oil runs back out). This should equate to around 1.1 litres.
6. Refit the filler plug and again take care not to over tighten.


Dispose of the old oil at a local garage / workshop / recycling centre.

The whole process tool me around 90 minutes.



I could not find any Mercedes recommended service intervals for these oils but I do know that the "life time" oils thing from manufacturers is not good. Not changing the oil until something fails will of course make it "life time" but said life will be a lot shorter! Oils degrade over time and they carry increasingly large amounts of debris. This reduces bearing, gear and synchro life.


Here are the pics for transmission and diff, fill and drain plugs.
Pic #1 : Manual transmission viewed from the right side of the car
Pic #2 : Diff fill plug viewed from left side of the car
Pic #3 : Diff drain plug viewed from right side of the car


I was not satisfied with the gear shift smoothness using the Redline MTL so I replaced the transmission fluid with Castrol Syntrans V-FE 75W-80. This is lot better. Shifts very smoothly now. :smile:
 

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Discussion Starter · #3 ·
Pictures are needed to understand to me.
Specially at step 5 in Transmission and step 1 in Differential.

Thank you anyway.

It's very straight forward. The only plugs requiring a hex key are the transmission drain and fill plugs. When under the car you'll find them as described. Next time I'm under car, I'll take some pics.
 

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Registered 2016 SLK55 AMG
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...
I was not satisfied with the gear shift smoothness using the Redline MTL so I replaced the transmission fluid with Castrol Syntrans V-FE 75W-80. This is lot better. Shifts very smoothly now. :smile:
What size hex keys are needed? They look rather large in the pictures and I'm not sure my set goes big enough.
 

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2005 SLK350
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Find the right size bolt, put some nuts on it and make your own drain plug removal tool. It's worked for me in the past.
Insert the head of the bolt into the hex recess on the plug. Use the nuts on the bolt to apply torque and remove the plug.
 

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Registered 2016 SLK55 AMG
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Find the right size bolt, put some nuts on it and make your own drain plug removal tool. It's worked for me in the past.
Insert the head of the bolt into the hex recess on the plug. Use the nuts on the bolt to apply torque and remove the plug.
Clever!

I never heard of that trick before. I've used two nuts for other things...

... like removing exhaust manifold studs. >:D
 

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Volkswagen uses 'special tools' for all sorts of things. Sometimes they are an absolute necessity, often times not.

Fahvernugen is supposed to mean "driving enjoyment" but I think it actually means "expensive repair".
 

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Registered 2016 SLK55 AMG
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What size hex keys are needed? They look rather large in the pictures and I'm not sure my set goes big enough.
answered my own question... 14mm hex on the rear transaxle (both drain and fill plugs), 14mm on the transmission fill plug and 17mm on the transmission drain plug.

Good thing I ordered a large set of 1/2" drive hex sockets... came today and the fluids are draining overnight.
 

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2006 SLK280
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I completed this job last weekend. Some notes from my experience:
  • The gear oil for this job available in the US is A001989330312, made in Germany, probably by Fuchs. It comes in 1.0 L containers, you will need two for the job. Despite the 1.0L capacity of the differential, I ended up using about 1.4L due to spills, oil left in the transfer pump, etc.
  • Wear latex gloves and clothes you don't mind throwing away. Getting the MB gear oil on yourself is the DIY equivalent of getting sprayed by a skunk.
  • The oil I drained out was very dark at 67k miles. I plan on changing the oil every 50k miles in the future.
  • Posts on other MB sites imply that the differential can be overfilled if the oil level is checked when the car is lifted and the rear suspension is hanging. I performed the fill with the rear wheels removed and the car suspended and level. I then rechecked the oil level with the weight on the rear wheels. I did not notice any difference in the oil level when the rear suspension was hanging vs. supporting the weight of the car.
  • A set of socket extensions was very helpful to access the drain plugs around the exhaust and underbody braces. A transfer pump is required to pump the new fluid in, the differential sits too high to tip the oil bottle up while under the car.
  • The WIS recommended torque for the drain plugs is 50 Nm.
 

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WARNING!!!

Remove the fill plug Before you drain the Transmission or Differential.


There have been cases where the fill plug couldn't be removed, or is extremely difficult to remove.
If you drain the Trans or Diff, and cannot fill it, Well Nuff said..
 

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Registered 2006 SLK55 AMG
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No need for a transfer pump for the differential in the 55 AMG. The bottles include a small nozzle feature and are designed to be squeezed. Lastly, there actually is sufficient room to get the bottle right up to the fill port.

I ended up spilling a bit, but as previously observed I needed about 1.75 bottles worth, so spillage is included lol.

I had a long snipe and was prepared to wrestle a bit, but neither plug was excessively tight.

tn
 

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2005 SLK350
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Another option on refilling the gear oil is to get a few feet of clear vinyl tubing. Get the largest diameter you can that will fit inside the fill hole. Feed the tubing so that the low point is the end at the fill hole and then run it out from under the car so you can stand outside the car and squeeze the gear oil through the tubing and down to the fill hole. If you know how much you need and you are a little careful you can have it all run down the tube and not waste any. Since the tubing is clear you can see when it has all flowed into the trans/diff. Leave your drain/catch pan under the fill hole to catch any small amount that might come out of the fill hole.
 

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Discussion Starter · #18 ·
I notice in the pictures the nuts have what looks like plumbers tap on the threads, is that correct?
Thanks Beppi.
I suspect that the threads on the car are metric. Many plumbers threads are not metric. The only way to be sure is measure with a thread gauge and Vernier gauge. Given the repair cost of forcing anything in there that is not the correct thread (or length) I would be VERY careful.

OK, I am curious, why do you ask?
 

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Registered 2006 SLK55 AMG
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I think Beppi meant that the plug had teflon tap(e) on it? Yes/no? If so, then I can state that mine did not have tape on it when I removed it, nor did I use tape when I replaced it. My two cents: teflon tape is not necessary in this application.

tn
 
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