So 2 weeks ago I pulled my 7 speed out and had my transfer case bearings done. I put it back in my car and the seal where the front driveshaft goes into the transfer case starts leaking. I take it to the shop that rebuilt the transfer case and they redid the job(FYI they lowered the back of the trans and did it on the car) so you dont have to remove to transmission to to the transfer case on w204s, anyway he changed the seal calls me that its done. I get home look under and it starts leaking again... A lot less then the first time but a leak is a leak, so I take it back, today he is disassembling the transfer case for the 3rd time -_-.. at 52.95$ a seal its getting pricey for him, although he can do the job in 1hour, is there a trick to it ? I see how its a guessing game because mercedes made it so you cant see the seal when you're installing the output shaft and the shaft goes in at an angle, is there a trick to this? The dealers have hundreds of those seals and people tell me it is very common for it to fail but whats the trick to install them ?

 

He\you need to look at the WIS docs or he will be doing the job ten times!!

 

Wish I had a WIS file but dealer wont give them out.

 

So I just got off the phone with my mechanic, 3rd seal he installs, after a test drive, IT FAILED AGAIN WOW, im losing hope seriously, now im stuck without a car for the weekend again , like this is a 40 year vet mechanic that specializes on german, someone must of went threw this if that seal is so hard to install..

 

anyone ? he is putting the 4th seal tmrw morning, he will check it with a bore scope before reassembly.. I dont understand why he isnt able to put the seal back..

 

Did you ever get this resolved? I just did a bearing job and have this same seal leaking.

 

Yes it was a rust ridge on the shaft where the old seal rides. When you go back to the shop that did it, tell them not the press the seal all the way in, leave 1-2 mm gap so the seal rides on a new/clean part of the shaft or replace the shaft but if the U joint is tight, there's no reason for that. We reinstalled that seal 2mm off and almost 3 years later, still leak-free with the same driveshaft.

 

Man, I appreciate the quick response for a 3 year old thread. I actually did the bearing job myself and it resolved the noise issue but this thing is leaking BAD from that seal now. What you said makes a lot of sense. The u-joint seemed good but the shaft and especially inside the u-joint were quite rusty. I didn't notice a rust ridge right there but I wasn't looking for that either.

That makes me feel a little better about digging in to do this job again. Hopefully that's the issue and I can replace the shaft / seal and get it back going.

 

Good luck, it wasn't really a rust ridge but more of a pitting issue. It had a very very slight amount of pitting where the seal rides and any imperfection will cause a leak there. When you install the driveshaft, make sure to put some atf on the seal and shaft before to avoid the seal from pinching.

Also if you can take a piece of thin plastic and put it around the shaft as you slip it into the seal to 100% be sure the rigdge doesn't tear the seal. Something like in this video at 0;22 - 0:40 f you understand what I mean ;

 

I appreciate the insight. There's a pretty dang good chance there's pitting on that shaft as there was a good amount of rust all inside the u joint.

I hate to effectively do this job over but at least I know what I'm looking at this time. My plan is to replace that gear that has the shaft on it to alleviate any rust issues entirely, since I have to dig back into it anyway, and of course replace that seal once again.

I seem to recall seeing that gear/shaft on the internet somewhere and I may have it bookmarked so I've gotta do some reading tonight.

Again, thank you for your response! Gives me somewhere to start!

 

Can you please give me this shops info to pick the brain of the mechanic that can get this done in an hour!