Andre91

I've been having an intermittent issue with a vibration being felt through the steering wheel when making sharp turns (full lock, or almost there) at slow speed and it was diagnosed as a faulty planetary gear set in the transfer case, with the front wheels turning at different speeds during a sharp turn the clutches slip excessively. The quote I received from a dealer is pretty significant due to the fact that the transmission pan is corroded and requires replacement to do a fluid change, and they want to replace the front section of the exhaust including the resonator because the flanges may not come apart (IF they don't come apart, is cutting it out and welding in new pipe not an option?). The exhaust and trans pan are almost $2000 of the quote, more than actually rebuilding the transfer case. I see I can pick up a good used trans pan from a southern car (no corrosion) for well under $100 shipped and there might be a possibility of salvaging the exhaust, so I'm going to get a second opinion from my independent guy.

How long am I ok to drive it in this condition while I decide what I want to do? The vibration isn't terrible, and it's only when making low speed turns, and starts going away the warmer it gets.

Quint22

Assume its the bearings, there is a thread here on rebuilding one. Dealers just replace the trans since its all integral so odd they would offer to rebuild that part. Definately get the independed to look at it. Probably stop driving it IMHO.

Andre91

They actually quoted replacing the gear set and clutch pack, and doing it in house. I actually had the transmission in my old GMC Sierra work truck completely rebuilt by the dealer under warranty, even though it probably should have been replaced as a complete unit (pump failed, 4th/5th/6th clutches destroyed due to loss of lubrication), so there are dealers out there doing transmission work but I'm sure not every one has the equipment or staff with the expertise in transmission work. I'm in Canada and parts prices are quite a bit higher than in the US, even after taking the exchange rate into account, so it may be more economical to repair vs replace in some cases.

Arrie

Why do they say it is the planetary gear problem? Does your transmission / transfer care make whining noise?

Vibration can be caused by the locking disk "stick-slip" condition when you make sharp turns and the disk must let front and rear axles rotate different speeds.

The center differential lock in these cars to my understanding is a "simple" spring loaded clutch that will allow movement under certain torque conditions between the axles. Because there is always some "spring" present in these systems you can get this stick-slip condition in the locking disk that cause vibrations.

Years ago, in this forum, there were people telling how they fixed this issue by jacking one wheel up and running the car with gear ON for a little bit to "clean" the differential locking clutch disk. Some people claimed this also worked.

I would try something like this myself first before letting someone do fix that may have nothing to do with your problem. If you run one wheel up, you can also hear if you really have the planetary gear problem as only one wheel up and turning will make the planetary gears rotate and they usually make whining noise if the bearing failure is present with them.

Andre91

It doesn't make any unusual noises at all, you can feel the vibration through the steering wheel and floor when turning at very low speed, but when it occurs there is no change in sound. Even on the coldest days this winter (-35c) I haven't even heard any pump whine, let alone the sound of a bearing going bad. Are the clutch discs part of the planetary gear set? They may be wanting to replace the entire assembly.

The best way to describe it is that it feels like making a turn in a truck with 4x4 engaged.

konigstiger

See attachments.

https://mbworld.org/forums/e-class-w...nsmission.html

Arrie

"The best way to describe it is that it feels like making a turn in a truck with 4x4 engaged." - That is exactly what it would feel like if it is the locking disk "stick-slip" that is going on. You not hearing any grinding sounds also speaks for it.

You could go find a big empty parking lot where you can drive circles with different radius. This should not damage the car as it was designed to be driven with wheels turned in any road surface. This would be doing kind of the "wheels up" test in a legal way. If it is about the disk surface needing some "cleaning" you should see the condition get better. If not, then it may well be the problem with the planetary bearing.

Andre91

So, just wanted to provide an update on this issue. After a long highway drive the vibration went away and hasn't returned so far, 1500km later. After two hours or so at highway speed (cruise set to 120km/h) I stopped for a coffee and noticed when I was going around a tight drive thru the vibration was gone. When I got to my destination I again noticed it was gone as I was making tight turns going around a parking garage. When I left to go home, same thing, no vibration. It hasn't happened since.

I do very little highway driving, I occasionally go for a 45 minute-hour drive on a nice day, maybe once a month, but other than that all of my driving is in the city. Could it just be a case of needing to get the transfer case up to temp and give it enough time to clean any buildup off the clutches?

Arrie

Yes it could.

There are people recommending center differential clutch disc cleaning by jacking one wheel up and running the car on gear for 10 - 20 seconds. This procedure is not recommended by MB but that would be the first thing I would do if I had a 4Matic and it would start acting up like that.

If the problem is with the bearing that has been found to be an issue in many cars this procedure does not make any worse but if it is about clutch disk surface condition it can be a big help.