Driveshaft vibration on 240D / 123 chassis
 

My 240D vibrates at certain revs when in drive. It seems to vibrate more under acceleration and at certain revs, not speeds.

The driveshaft support rubber where the spline joins the next part of the "propellor shaft" (as the germans like to call it) about half way between the differential and the transmission, is cracked and I can push the driveshaft a good 1/2 inch up and down in the supports, ie the driveshaft doesn't seem to be securely held in the supports and looks like it could wobble or 'orbit' in the supports. However, I find it hard to believe that those little rubber supports (kinda like a CV boot) could hold the driveshaft in place at high revs.

Is it the center bearing (pic attached or see at http://www.partsamerica.com/ProductDetail.aspx?mfrcode=BCA&mfrpartnumber=106&parttype=907&ptset=A) that holds the shaft in place?

I am assuming this driveshaft movement is bad, but am not sure, since I haven't seen any to compare it with. :confused:

If this is bad (the drive shaft moving 1/2" in the supports) then how do I fix it? Replace the driveshaft supports? Replace the drive shaft center bearing?

I have read various posts on this and looked at the MB shop manual (see http://skinnerbox.steaky.org/Service/W123/w123CD2/Program/Chassis/41-200.pdf ), but am confused as to what to replace, and more importantly, what it is called and where to buy it from. There are a few places on the web to buy parts called Driveshaft center support bearing (pic attached), or driveshaft support bearing, driveshaft support or driveshaft centerbearing.

HELP! confused! And want to fix it! Also, might it be the flexplate? How would I tell?

Thanks, and help would be greatly appreciated. I've worked on a lot of car things, but never a drive shaft! Feeling intimidated! :(

Half an inch deflection is too much. Year, that rubber really does help hold the center of the driveshaft . I would replace both the center bearing ( you have the picture) and the rubber mount (center support) that it fits into. Both together should run you no more than $30 on fastlane. I have done 3 of these and have the actual replacement of these bits down to 10 minutes. Be sure to mark the orientation of the rubber mount. If you haven't done the flex discs recently, this is a perfect opportunity to do them as well. Especially good to do this if you have a manual transmission where new rubber helps absorb some of the shock to the rear end and driveshaft.

Awesome!
 

Awesome, thanks for that reply! I feel like I can handle it now.

Sounds like I should replace the flex disc, center bearing and drive shaft support.

Then what's all that stuff in the MB Manual (see the pdf link from my previous post) about drilling holes and pulling things out?

Thanks for your help. Much appreciated, also the heads up on fastlane.

Paul

Paul,
Don't worry about all the hole drilling. That is for something else. All you have to do is mark the shaft before you separate it and check the condition of the u joint while the front section is off. The joint should move smoothly through all range of motion without any roughness except at the straight up position. Roughness passing through center is permissable on a shaft that has been in service for quite awhile.

Thanks
 

Thanks AutoZen.

Sounds pretty straight forward. I ordered a bearing and support and a flex disc (may as well while I'm at it). I'm sure I'll know what the U joint is when I see it.

Looking forward to less vibes from my baby! :D

The u joint is what you are going to slide the new bearing up to.

Ready, set, go
 

Thanks for the help guys.

The parts arrived today from auto warehouse and I'm ready to put them in tomorrow and lose my vibrations! I'll let you know how it goes. :D

Paul

Done, but still vibrating
 

I replaced the driveshaft center bearing and support, but the vibes are still there.

They seem to change though.

So I was going to replace the engine mounts, but they seem fine (and a friend said they look fine). But I'm not sure how you tell a mount is OK without taking it out? The engine wobbles at idle, but that's normal isn't it?

So I took out the tranny mount and looked at it, and it is pretty much new, and only maybe a 1/4" shorter than a new mount (I had the wrong replacement mount - the one with the funky W shaped hole) so I don't think it is that. But after putting the old mount back in, the vibrations are different. They don't seem to start until the car is warm, and then they are less.

Also, you can feel the vibration when the car is in neutral or park and you rev it up to about 1500-2000. It's like when you drive over a very rough road, or a good dirt road, or those things at the side of the road that wake you up or snap you out of it if yuo're drunk.

What could it be??? Engine mounts? How do I tell if they're good without taking them off? My assumption is it must be the engine or transmission since I feel the vibes even when it is in neutral and standing still .

Any ideas?

Thanks.

...and here's the next member going nuts on those vibrations...:silly:
pdrayton, read this:
http://www.peachparts.com/shopforum/showthread.php?t=139680
I still couldn't find the problem, actually I was about to change flex disc, center bearing and driveshaft support. But since it didn't fix the vibes in your car - I don't know...

Ja, read that...
 

Ja Airbus Taxifahrer,

I read your posts, but looks like you still haven't fixed yours either.... what could it be....

Since it appears your 240D has an automatic transmission...

(copied from **************.com web page)

"Diesel Engine Transmission Torque Converter Flex Plate Failure

The center of this spring steel flex plate is bolted to the rear crank shaft flange. The outer perimeter of the plate is attached by six bolts directly to the torque converter which in turn drives the transmission input shaft. Although similar flex plates are used on gas engined Mercedes the flex plate problems I have seen have always been mounted to diesel engines. I believe the reason for this is due to the higher vibration levels and the harsher compression kick inherit in the diesel engine.
I have discovered cracks in the plate, loose bolts and in the most severe failure to date a completely destroyed flex plate as pictured here. This severe failure as well as other problems I have encountered seem to start with one or more of the six perimeter bolts loosening up. The first sign of loose bolts may be a clicking or ticking noise in the engine. It may even sound like a bad injector or a loose valve. If the bolts fall out or the flex plate breaks as shown here it can sound like the engine has a failing connecting rod or broken piston. The noise can be loud and can fool you or your mechanic. If you experience metallic engine sounds that you can not isolate be sure to check your flex disk for cracks and bolts for security. There is a steel plate or oval plastic plug just aft of the rear of your engine oil pan that you can remove to inspect the plate and check the tightness of the bolts.

Note: When replacing these critical bolts I always use Loctite thread locker or equivalent. Each bolt should have a flat washer as well as curving spring steel lock washer. The lock washer should go between the head of the bolt and the flat washer. If you find or suspect loose bolts go ahead and remove them and reinstall with Loctite (purchased at any local auto parts store) and the proper washers. If you use washers that are too thick the head of the bolt can hit the bell housing also causing bad metallic noises. Do not ignore this flex plate!"

Easy to check and just a thought and since your engine vibrates in neutral at various rpms. Mark

Hey, this a very interesting thesis. I will check this asap. Thanks a lot! Could you maybe put some pictures here where exactly to check?

It's pre-driveshaft
 

Thanks for the info guys.

However, I don't understand how it could be the flex plate when the vibrations are there when the car is in neutral.

The flexplates are on the driveshaft after the transmission, so the driveshaft, and hence the flexplates, don't have any stress when the car is in neutral.

To me that means it can't be the flexplate. Or am I misunderstanding the situation here??

You are confusing flexplates with flexdiscs. On MB's one flexdisc (rubber disc) is located between the output flange of the transmission and front of the driveshaft and another one is located between the rear of the driveshaft and the input flange of the differential. The flexplate is a stamped steel plate with ring gear that is bolted to the rear of the crankshaft and the front of the torque converter on automatic transmission cars only (it, together with the torque converter, take the place of the flywheel on a manual transmission car). Although airbus said his car was "manual everything" he did say when in "park" so I assumed he has "manual everything" except for his transmission. Mark

thick
 

Well, the plot thickens....

Sounds like a difficult thing to get to....this flexplate. Can I get to it without taking off the tranny? And, could it be contributing to a whining that sounds like it is coming from the tranny of diff?

I'll have a look under the car.

Did I see right, hookedon210s, you're in Jacksonville FL