How to replace the driveshaft support (carrier) bearing - A step by step guide
 

Step 1: Mark the relative positions of the front and rear driveshafts. Also mark the relative positions of the front and rear flex discs.

Step 2: Get a 46mm and 41mm wrench and loosen the sleeve nut located on the front section of the shaft.

Step 3: Remove the front flex disc and compress the driveshaft.

Step 4: Remove the front portion of the drive shaft.

Step 5: Remove the two 13mm bolts on the carrier support bracket.

Step 6: Note the circlip. You will need to remove this later.

Step 7: Remove the rear flex disc and remove the rear portion of the drive shaft.

Step 8: Picture of front and rear driveshafts removed and associated parts. The broken portion of my carrier bearing and bracket are still attached to the rear driveshaft.

Step 9: Remove the circlip. Get a large three jaw puller and remove the carrier bearing.

Step 10: Picture of rear driveshaft with old carrier bearing and bracket removed. Also pictured are the new carrier bearing and bracket.

Step 11: Press the new carrier bearing into the bracket. I lubed the bracket with dishwashing liquid and pressed the carrier bearing in with my hands.

Step 12: The new carrier bearing and bracket are installed on the driveshaft. Don't forget to reinstall the circlip! The bracket has a shoulder which must face the rear of the car upon installation. The bearing rests against the shoulder when you press it into the bracket. Picture it like this - if you were to pull the bracket off the driveshaft, it would take the carrier bearing with it.

The last picture is of the gigantic wrenches you will need. Many of your parts/bolts may be rusted in place so be patient. My rear flex disc was seized to the driveshaft so I had to remove the flex disc from the differential to get it out of the car. You may be luckier than I was. Make sure you realign everything to match the marks you made upon installation so nothing is out of balance.

Good luck!

Scott

Nicely done.

Good job. Great write up.

Thank you for the write-up.

You can get a big adjustable wrench at a plumbing supply store. I got mine at lowes, it opens very wide and has about an 8" handle.

dd

I just did this job two weeks ago on my '85 300TD and I needed a few extra steps. The manual advises disconnecting the parking brake cable and supporting the transmission from below in order to remove the transmission support. I took both of these steps. The parking brake cable can probably be worked around, but I did find it necessary to remove the transmission support to get better access to the bolts on the front flex disc. Also on my '85 there is no snap ring on the drive shaft. On the later year models there is another ring in it's place that is held on by friction and it requires the use of the bearing puller to remove the carrier bearing and the ring at the same time. I also had the car in neutral most of the time so that I could rotate the driveshaft by hand from underneath in order to access all of the flex disc bolts. Just be sure to use sturdy jackstands under the car. Overall it was not a difficult job, but it did take me a while and I had to spend quite a bit of time rolling around on my back under the car.

Thank You
 

You made it look easy!

My car is a 4-speed manual and that may make a difference. There certainly are different ways you can go about it. This just lays out the basics and most people should be able to figure it out from there.

Scott

I certainly did not mean to imply that you had done anything improperly. I just wanted to point out potential differences for other folks that might be thinking about doing the work. I actually wish I could have seen your write up and pictures before doing my own. It would have saved me some time under there figuring out what was what. Thanks for the write up and pictures.

Bookmarked! Thank you.

It's in the Wiki
 

This DIY is now in our DIY Wiki HERE.

Thanks Scott!

Nice job! I needed that. Mine needs done to.:)

Is a w126 drive shaft bearing replacement the same?

Why??
 

What are the symptons to make you replace this?
I have been experienceing some "clunking" that sounds like it is coming from the middle to the back of my car. Could this be a remedy?

1983 300SD

Thanks

Tim

Man.... I really could have used this last month!

Thank you for doing a detailed write up. We need more stuff like this in the DIY area.

Good job!

Clunk from rear
 

Hey TC_300SD - Is your clunking around 20 - 25 mph while taking your foot of the accelerator pedal like mine? Can't figure this one out, may need to go into indy since i'm recovering from rotator cuff surgery and can't use right arm.

Anyone else have a guess - sorry to hijack

Clunking
 

Yes, defintely only at lower speeds, have to get it in the air to check it out, but thought this may be a solution.

Let me know if you get it into your indy and what he says about it.

Tim

I just got all my parts to replace the flex plates & carrier bearing.

Two questions.
1. I got a driveshaft boot. Where exactly does that get placed ?

2. The flex plates came with allen head bolts instead of hex heads. See
any problems with that?

---------------------
1984 MB 300SD Turbo

has anyone done this on a 123 coupe, my sleeve nut is inside the tunnel over the welded support. i really dont know how wrenches this big will fit on an angle in there.

It'll fit. There isn't much room and you won't be able to turn it a lot, but the good news is you'll only need to turn it a little.

Scott

Did the new bearing go on the shaft easily?

Yes. I was able to slide mine on with my hands after lubing it with dishwashing liquid.

Scott

I helped a member replace his bearing a while back and it required driving on the shaft. Wasn't fun... ended up taking it to a shop and having it pressed in place.

I have a new bearing for my wagon in hand but have putting the job off due to past experience. We'll see how it goes.

Thanks.

whatever i did the sleeve nut wouldnt come loose, i broke a 11mm wrench trying to wedge the driveshaft and then it wouldnt loosen with a 12" adjustable wrench on the inside nut and huge channel locks on the outside.
so i gave up on the sleeve nut, i was just dropping the diff and i thought i would need to loosen it but i didnt.

I'm a little confused over the orientation of the bearing support ... you said the side with the little "ledge" that the bearing backs into should face toward the rear of the car, which makes sense, but mine was facing the other way when I took it off the driveshaft. And the picture in the manual looks like mine did. In this picture, which direction should this side of the support face?
http://12.153.160.115/images/catalog...1234101081.jpg

Re-read POST # 3 & see picture # 3.


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1984 MB 300SD Turbo

I have the exact same issue. It's at the indy now, I'll let you know what he says

Step # 3 was to remove the flex disc and compress the driveshaft ... :confused: I'm assuming you meant step 12, which I read carefully but just want to clarify if I'm reading it right.
In my AllData manual, it states "Install rubber mount in such a manner that inner V-fold points toward universal joint." This is the diagram ... I have marked in red the "shoulder" that the bearing sits up against, and the direction that is front of the car. It looks like that is opposite of what is described/pictured in step 12 ... if I'm reading that step right, it says the shoulder should face the rear of the car. I'm not saying the DIY is wrong ... more likely, I'm reading something wrong, so I'm looking for clarification. I really don't want to do this wrong and have to take the driveshaft apart again. Ever.:o

Sorry. It was POST #3.


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1984 MB 300SD Turbo

Ah, that makes more sense. Still, the picture and description are opposite of the way mine was orientated on the car, and the way the manual depicts it above.:confused:

Would installing the carrier "backwards" cause driveline vibration?
I replaced mine and put in the new one according to my Haynes manual.
I now have a wicked vibration that starts at about 40 mph and peaks at about 55 mph. Very annoying.

I did my driveshaft about two weeks ago. Here is a link to a thread I started. Has some good pictures. I copied some of the pictures and the step by step write up and took it with when we did the shaft.

http://www.peachparts.com/shopforum/diesel-discussion/250866-question-flex-disk-change.html?highlight=flex+disk


---------------------
1984 MB 300SD Turbo

Thanks, the extra pics helped ... and they jibe with the manual pic I posted and the way my support was assembled when I took it off. The "shoulder" on the support is closer to the front of the car. The "V" points toward the rear.

That high school wrestling newspaper page in the pics reminds me of the old newspaper I used to work at .. yikes.

The diagram of the direction of the carrier bearing support is correct. The V fold points toward the rear.

The cir-clip has bent tabs. The proper installation of the cir-clip is with the bent-down tabs toward the ring in front of the u-joint.

If the halves of the DS need to be separated or not depends upon the model (engine type).

Removal of the 46mm nut can be accomplished with just one 46mm wrench (or one big adjustable). Just have a helper inside the car press on the brake or select Park (auto trans) each time you rotate the DS while losening the nut.

thump thump thump
 

my '84 300d is making a thump thump thump sound, 16 to 19 mph, under acceleration. doesn't seem to matter what gear.
my lead foot makes it worse.
is this a symptom of carrier bearing failure?

propeller shaft
 

fruitcakesa,

An Old Arthur Dalton trick is to roll the chassis back and forth 10-15 feet on it's
wheels BEFORE tightening the Clamping 46MM nut.(It "Settles" the driveline.)

Propeller Shaft
 

brihawali,

'Also might be one of the flex discs.

Ignore things that go Thump,Thump,Thump at your own risk!

thump thump thump
 

the bearing was fine.
the holder was shredded.
both renewed,
thump gone.

Actually this isn't a trick at all. I don't know why MB doesn't mention this in the W123 maintenance library, but it's in the W114/115 manual. And the rolling, by just a couple of feet, should be done a few times with both the 46mm nut and center support not tight. Then tighten the nut followed by the center support.

This procedure must be done, followed by the tightenings, with the car on its wheels. If the procedure is not done, the amount of difference is minute and any stress can usually be taken up through the rubber center support - it's quite flexable. Omitting this procedure will not cause any drive-line vibration.

I just did the carrier bearing swap, and it took me about 3 hours. I was able to easily slide on the new bearing after heating it up in boiling water, and sliding it on a frozen shaft end, no pounding at all.

Does the car really have to be on it's wheels and roll back and forth, or I can just take the shortcut by just spinning the wheels a couple of times, clockwise and counter while the car is up on jack stands?

This is not a recommendation not to do the rolling thing. But, when I did mine a few weeks ago I had the Car on Ramps in the Front and Blocks under the Back Wheels. The Ramps kept me from rooling the Car.

I tightened up the Coupling Nut and did not roll the Car. I figured If any problem showed up I would go back and loosen the Coupling Nut an Roll the Car.

Part of the reason for not rolling the Car was my Wrench is a over 2.5 foot long combination Wrench; no room to tighten or loosen anything while the Car sits on the Wheels and I was in a big hurry to test drive the Car because I had also changed the B2 Piston and wanted to know if that part of the job worked.

So as it turned out I am having no issues with the Driveshaft or vibration and will leave it alone for now.

I didn't do the rolling either.
Also probably misaligned the splines,
as I had rubbed off my marks.
(don't use a wax pencil)
All seems fine, couple thousand miles later...

Bearing Boiling
 

Frybenz,

I would like to know the Long Term results of your Bearing Installation Method.

"I just did the carrier bearing swap, and it took me about 3 hours. I was able to easily slide on the new bearing after heating it up in boiling water, and sliding it on a frozen shaft end, no pounding at all."

(Say in about 20K miles)

Thanks!

[QUOTE=Scott98;2176606]Step 10: Picture of rear driveshaft with old - if you were to pull the bracket off the driveshaft, it would take the carrier bearing with it.

The bearing rests on the mount shoulder when pressed in. The mount shoulder is adjacent to the shaft circlip when installed. If the mount were pulled off it may leave the bearing on the shaft. The mount deep V should be facing the differential.

I was under the impression that one would press the bearing into the rubber support mount prior to installing the bearing/mount onto the drive shaft. For the user(s) who mentioned placing the bearing in boiling water, did you install the rubber bearing mount after you installed the bearing on the shaft?

Or did you place the bearing/rubber mount assembly into a few layers of freezer zip lock bags, of which was placed into boiling water? If that is the case, would not the high temperature degrade the rubber components?

Analogous to your heating method, can the drive shaft centering sleeves at the front and rear of the drive line be frozen to ease with installation?

For those who did not use the hot water trick, how did you press the bearing onto the shaft if the soapy water was insufficiently slippery for the job?

On my 1979 240D, the rubber V-channel on the outer-most portion of the support has the narrower end of the V pointing towards the U-joint. Meaning that if the bearing-to-rubber support interface was all loose, the rubber support would pull off the spline-end and leave the bearing behind. There seems to be conflicting views on how this should be installed. I am not sure why.

Lastly, I was able to separate the splined intersection of my drive shaft without loosening the 46 mm nut. This seems to imply that I've been driving around with an untightened centre nut. What damage could this cause?

Is the reason for tightening the centre nut while the car is on all 4 wheels to set the proper drive line length for flat level operation? What about the cases when the car goes over bumps? On my Jeep, the drive line is meant to extend and contract with the terrain. Why is this not the case with these W123 vehicles?

Thanks a lot!