NYCGLK

Hi all,
I have GLK350 4matic that I have had for almost 12 years since new. At 105k miles now and I'm having faint buzzing noise coming from transfer case area. It more audible inside. I am guessing that the time has come for one of the TC bearings that have been an issue on 4matics. Anybody here replaced bearings in the TC? Any tricks or tips or threads on this? I found all necessary workshop manuals and got bearings and transmission service kit. Of course MB manual calls for transmission remove, but I know they like to complicate things to give dealer 20 hours of work for something that needs 5 hours. So I wonder if tranny removal is really necessary. I found one video where a guy removed TC from S-class without dropping tranny...on jack stands! I have a lift and liftcart so dropping tranny would be NBD if really needed.
Anyways, appreciate any tips or tricks anybody might have.
Cheers,

KEY08

Subscribed. Sorry, I have no information for you, but want to track this thread. Good luck!!

MBNUT1

Sounds like about the right timing for a failure of the transfer case. Mine went out the first time at 118K miles.

I did not do the work on mine but had it done by an indy. The indy then needed to rebuild it again a year later because he indicated that they were learning how to set the clearances properly.

They did not remove the transmission. They dropped the back end (removed the transmission mount and disconnected the drive shafts.) and let it hang from the engine mounts and removed the transfer case from the back of the transmission.

NYCGLK

lol great! I hope the second rebuild was on them. I guess that's why dealers say..."the whole tranny comes out".
I'm not sure what tolerances he is talking about. I'm not doing a "rebuild" just replacing 4 bearings unless they can be fitted a bit off. I will check the factory location.
I think the key is to prefill the TC...it relies on the supply of tranny fluid and I'm not sure how quickly or readily it gets into TC. Given the fact that it's an afterthought and these thing fail so quickly, it's not very well lubricated part.

MBNUT1

Second rebuild was on them. For the my car when the dealer is saying the whole tranny comes out they are saying you need a whole new tranny because they will not service the TC alone. The indy told me that the bearing that fails is undersized. All the indy did is replace a bearing. On the second replacement they kept getting difference shims machined to set the bearing clearance as they thought that the first time failed prematurely because the clearances were set too tight. On the first rebuild I had the transmission fluid replaced but not the second time. The indy says that fluid flows into the tc from the transmission and once it reaches a certain level such that it is above a dam if you will in the tc it flows back to the transmission.

Arrie

The problem is probably with just one bearing but if the transfer case is out for service you may replace more than just one of them. As MBNUT 1 says it is undersized bearing or bearing clearance is set too tight at factory. Bearing must have enough clearance for the shaft to expand axially. Bearing should not completely "bottom out" before the shaft temperature is at it's highest temperature. Also, the ambient temperature changes the case dimensions so it is not necessarily that simple for the clearance.

Also, when the bad bearing is out you can read the number on it. Very many bearings are made with the same physical dimensions but with different load bearing capacities. There is a chance that you can replace the bad bearing with one that has more or bigger rollers and can carry much more load.

Price of bearing is very low so whatever bearing you choose does not make difference in repair cost hardly at all.

NYCGLK

HI guys...posted some updates here for those following:
https://mbworld.org/forums/glk-class...anny-diff.html

Interesting about bearing tolerances. I'll have to take some measurements.

MBNUT1

Great post. Were the transmission fluid changes performed on time?

NYCGLK

Yea did the first one at dealer and second one at 90k miles we did ourselves and drained torque converter, which holds a lot of fluid.

I also did front and rear diffs at 90k miles which I highly recommend doing. Probably good thing to do with every other transmission flush.

MBNUT1

So my question was a leading one. I expected that you did maintain it properly. Just shows that it was a crap design.

NYCGLK

yep that TC is a cost cutting after thought with what seams like inadequate lubrication. But I must admit that simplicity is nice and other german car makers are not any better.
Although there seems to be sprayer for the two main gears so lubircant is directed in to the TC and the fluid was nice bright red so it's fresh. I'm not sure if the hole by the front output shaft is feed or return (I assume return) so then the failed bearing gets the fluid last.

NYCGLK

Did they use the right bearing during the first time? TIMKEN ones?
There are shims from the factory that determine the depth of the outter race. I will measure the thickness of the race on the old and new bearings. If they are the same and the current bearing lasted 105k miles I don't have impression this was tolerance issue. As you see incorrect tolerance with create issues sooner. What sucks is their mistake could have cost you the transmission. How much time since the second rebuild?

MBENZTECH

The big issue here is that there are no parts or information available from Mercedes to perform this repair. I have rebuilt many of the RWD 722.9 transmissions but the ones with the TC built in I leave them alone. The bearings kit should come with their own shims and they have to be pressed into the casing.

NYCGLK

Yea MB tells you to replace the tranny lol. Although there is manual for TC replacement which indicates that replacement transfer case is available as a kit. I haven't looked closely at bearings yet (I have a day job...wrenching and racing is hobby) I just went by what FCPEuro puts together.
I think you you are right, shims should come with bearings, based on your application. From videos, it looks like shims are lose (no need to press). So the big assumption here is that factory tolerances were correct and that replacement bearings are the same size.

MBNUT1

The second rebuild was done in January. I have only put a couple thousand miles on it since then. I do hear a whine upon deceleration in the 50 mph range.

The first rebuild service invoice states Timken bearing on the parts list.

Yeah I was scared both times that I was going to lose the transmission. It seems to work ok.

MBNUT1

Not sure I agree with that. Drove my '98 A4 Quattro from 30k to 220k without this kind of major league driveline failure. That included two track sessions with the Porsche club and my teenage son driving it. I can only imagine the abuse that he put it through. Under the heading of full disclosure Audi put two turbos and control arm bushings on the car during the warranty period and I had two wheel bearings and a steering rack installed and I put an axle in the car which was due to torn boot.

pierrejoliat

So Mercedes uses bearings made in Canton? Wow! I have met the Timkens, nice guys.
Also, as I'm sure you are aware there are many different durability, load, pressure and styles of bearings exactly the same size.

MBNUT1

I am somewhat aware as a retired engineer (my thing was dynamic system design (controls / hydraulics). I did talk to one of our engineers at work and he made me aware of what you are talking about. I relied on my indy who is supposed to be the best in town to make the parts selection. Lord knows I paid him enough to do it properly. This is somewhat painful because my son who is a chief engineer on mega yachts implored me to rebuild it myself but weather was crap which meant laying under the car in the cold garage was not my idea of a good time, I was under the gun at work and didn't really have a spare car to deal with it at my leisure.

pierrejoliat

I am a mostly retired distillation engineer by trade, we also do fermentation, I completely understand not doing it yourself, I feel the same.
One of my projects was Re-opening the Schoenling/Hudepohl brewery in downtown Cincinnati as a Sam Adams. Loved those "Little Kings"

MBNUT1

I am doing fermentation in the form of trying to make sourdough bread.

pierrejoliat

LOL good for you!

NYCGLK

actually made in France.
Not going by size, going by the exact part number.
Don't get me started on this.... There are 7 ways to set the tappered roller bearing. Projecta-set or torque set is what it seems to be from one Timken manual. So I think this is done by germans in white coats. I will go with measuring that everything is the same size and looks good. One new outter race I wasn't happy about so getting another and a spare bearing in case I screw something up. Some more pics coming later. I got to races off.

NYCGLK

Some of them got lucky here and there.

NYCGLK

A mini update back here:
https://mbworld.org/forums/glk-class...anny-diff.html

Arrie

Tapered roller bearings have three types of forces to deal with: The radial force caused by the gear mesh between mating gear wheels, the axial force caused by the gear mesh (helical) between mating gear wheels and sometimes problematic axle (or shaft) heat expansion. Everything else above is quite easy to calculate but the heat expansion. Heat expansion is difficult as the ambient temperature has a role in it.

If I would be doing the job I would err on the "loose" side on the bearing clearance as I would think the good MB engineers got the calculations right for forces but the data for the heat expansion was wrong.
Also, a too loose bearing does not fail unless it is way too loose and before that happens the gears probably are gone first.