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  #1  
Old 04-12-2019, 02:07 PM
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Thumping vibration from rear

Like the title says, I'm getting a thumping type vibration frm the rear of the car, but only when it is under load. Car is a 1983 300D with 336K miles. If I accelerate gently from a stop or am cruising, no problem. But if I accelerate briskly or am going up a steep hill and give it some pedal, I get the thumping vibration. Once it starts, if I let up on the power it goes away, give it more power its back. Once the load is gone, all is ok. Doesn't feel like tranny slip as the RPMs never fluctuate. Rear shocks are a year old and look fine, rear sway bar and end links are fine, and driveshaft carrier bearing is new (car was starting to thump before it was replaced anyway). Transmission mounts, rear diff mount, and motor mounts were all replaced to eliminate the problem, but no dice. So, could it be the rear axles? No visible tears or leaks in the boots, but they look original to the car. What about the U-joints? Help!

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  #2  
Old 04-12-2019, 02:11 PM
Shadetree
 
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Does it seem to come from between the front seat and just behind the console?
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  #3  
Old 04-12-2019, 02:26 PM
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Yeah, a little bit, but mainly more towards the rear seat
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  #4  
Old 04-12-2019, 03:14 PM
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Sounds like your driveshaft support bearing is toast. They aren't very expensive but the driveshaft has to come out. Make marks on the driveshaft to make sure you alignment in proper orientation as as not to affect balance.
This would be a good time to replace the front and rear couplings as they also contain rubber.

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  #5  
Old 04-12-2019, 03:21 PM
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Quote:
Originally Posted by psaboic View Post
driveshaft carrier bearing is new (car was starting to thump before it was replaced anyway).
Quote:
Originally Posted by Clemson88 View Post
Does it seem to come from between the front seat and just behind the console?
Quote:
Originally Posted by dieselworks View Post
Sounds like your driveshaft support bearing is toast.

There seems to be an information disconnect here!
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  #6  
Old 04-12-2019, 04:02 PM
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When the driveshaft was out, did you check the U-joint for notchiness or stiffness? The U-joint vibration will be much greater than a thump or wobble from a tire. An axle shaft will feel about the same as a tire that has a problem.
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Old 04-12-2019, 04:44 PM
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This has flex discs, yes?
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  #8  
Old 04-12-2019, 05:05 PM
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The flex disc or coupling could be the problem. Get the car up and check the front and back. If one is bad then change both.

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  #9  
Old 04-12-2019, 06:43 PM
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Originally Posted by Diseasel300 View Post
When the driveshaft was out, did you check the U-joint for notchiness or stiffness? The U-joint vibration will be much greater than a thump or wobble from a tire. An axle shaft will feel about the same as a tire that has a problem.
Where is the U-joint on these?
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  #10  
Old 04-12-2019, 08:18 PM
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Forgot to mention, car also has newer (within last 15,000 miles) front and rear flex discs. Did them the same time as the carrier bearing, and car was only occasionally doing the thump then, but now it is definitely getting worse. All mounts, flex discs, carrier bearing, etc were changed to try to fix the random thump. As for the U-joint, yes it was a little stiff, but didn't feel notchy. Looking back I probably should have changed it while I was in there, but didn't have access to a press to remove it. If bad axles feel like a bad tire, the they are probably still ok, As the car cruises down the highway rather smoothly.
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  #11  
Old 04-12-2019, 09:51 PM
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Ask anyone if they have ever had new parts fail? I know I have.

Taking a look at both Flex Discs and another look at the driveshaft Support bearing.

A different vehicle but I safely jacked (and chocked/blocked the front wheels) the rear wheels of my Volvo Diesel Car off of the Ground and started the Engine and put it into gear and let the wheels spin.
In my case it turned out to be the Driveshaft Support and I could see the Driveshaft bobbing around and was able to pinpoint the noise.

Concerning the U-joint. It is not supposed to be replaceable but others and myself have done it. There is threads. A new U-joint back when I did it was around $20 I bet it is around $30 now.

In the past there was places that would rebuild your drive shaft but as time has passed they seem to have disappeared as fare as Mercedes go.

Someone posted on another site that stiffness/notchieness can be taken care of without changing the U-joint. Essentially you get penetrating oil inside of the U-joint a flex it and beat on it with a plastic hammer till it is goose loose again. I can't remember how he said to re-lube the joint.

Sticking U-joint causes Vibration that Rips up several Drive Shaft Supports turns out to be Rusty Needle Bearings
W123 Propeller shaft vibration tears up rubber mounts, replaced nearly everything


U-Joint 2005
Can you replace the universal joints????? - PeachParts Mercedes-Benz Forum
I am replacing my drive shaft U joint, 300D turbo, W123, I have ground off the stakes, pressed/removed the old joint, now need to find the replacement to install.
I think some one said a one from an old Ford Falcon ?
anybody know the correct application to install ?
it seems to be like a cap width ~ 24mm = ~ 15/16"
and a length of ~ 73mm = ~ 2 & 7/8"
I think he said it was for a Ford Mustang
I'm thinking early 80's

Tightening Drive Shaft Collar Nut 2011 post #40
How to replace the driveshaft support (carrier) bearing - A step by step guide - Page 3 - PeachParts Mercedes-Benz Forum

My U-joint Repair thread 2011
Drive Shaft U-Joint Is Staked/Crimped In Place, Now What To Do? - PeachParts Mercedes-Benz Forum
My Benz World post with all of the U-joint sources.
http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1581728-another-u-joint-driveshaft-thread.html#post4677977

This cold be a repeat of the sites but my notes are a mess:
My U-joint replacement on Driveshaft at peachparts
Drive Shaft U-Joint Is Staked/Crimped In Place, Now What To Do?

Benzworld U-joint stuff part number is 900 410 00 31 (it is a made in Japan GMB U-joint part number 220-7289 #2 post has info

http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1581728-another-u-joint-driveshaft-thread.html
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  #12  
Old 04-12-2019, 09:51 PM
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Location: Long Beach,CA
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Ask anyone if they have ever had new parts fail? I know I have.

Taking a look at both Flex Discs and another look at the driveshaft Support bearing.

A different vehicle but I safely jacked (and chocked/blocked the front wheels) the rear wheels of my Volvo Diesel Car off of the Ground and started the Engine and put it into gear and let the wheels spin.
In my case it turned out to be the Driveshaft Support and I could see the Driveshaft bobbing around and was able to pinpoint the noise.

Concerning the U-joint. It is not supposed to be replaceable but others and myself have done it. There is threads. A new U-joint back when I did it was around $20 I bet it is around $30 now.

In the past there was places that would rebuild your drive shaft but as time has passed they seem to have disappeared as fare as Mercedes go.

Someone posted on another site that stiffness/notchieness can be taken care of without changing the U-joint. Essentially you get penetrating oil inside of the U-joint a flex it and beat on it with a plastic hammer till it is goose loose again. I can't remember how he said to re-lube the joint.

Sticking U-joint causes Vibration that Rips up several Drive Shaft Supports turns out to be Rusty Needle Bearings
W123 Propeller shaft vibration tears up rubber mounts, replaced nearly everything


U-Joint 2005
Can you replace the universal joints????? - PeachParts Mercedes-Benz Forum
I am replacing my drive shaft U joint, 300D turbo, W123, I have ground off the stakes, pressed/removed the old joint, now need to find the replacement to install.
I think some one said a one from an old Ford Falcon ?
anybody know the correct application to install ?
it seems to be like a cap width ~ 24mm = ~ 15/16"
and a length of ~ 73mm = ~ 2 & 7/8"
I think he said it was for a Ford Mustang
I'm thinking early 80's

Tightening Drive Shaft Collar Nut 2011 post #40
How to replace the driveshaft support (carrier) bearing - A step by step guide - Page 3 - PeachParts Mercedes-Benz Forum

My U-joint Repair thread 2011
Drive Shaft U-Joint Is Staked/Crimped In Place, Now What To Do? - PeachParts Mercedes-Benz Forum
My Benz World post with all of the U-joint sources.
http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1581728-another-u-joint-driveshaft-thread.html#post4677977

This cold be a repeat of the sites but my notes are a mess:
My U-joint replacement on Driveshaft at peachparts
Drive Shaft U-Joint Is Staked/Crimped In Place, Now What To Do?

Benzworld U-joint stuff part number is 900 410 00 31 (it is a made in Japan GMB U-joint part number 220-7289 #2 post has info

http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1581728-another-u-joint-driveshaft-thread.html
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  #13  
Old 04-12-2019, 10:12 PM
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Quote:
Originally Posted by INSIDIOUS View Post
Where is the U-joint on these?
It has a single U-joint that is behind the Drive Shaft Support Bearing. However, the front part of the U-joint has a splined shaft and the Drive Shaft Support bearing gets pressed on to that shaft which I said is the front part of the U-joint.
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  #14  
Old 04-12-2019, 10:23 PM
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This is a pic of my U-joint. Though I was not having any vibration issues I had removed the Drive Shaft when I did the B2 Piston Change on the transmission and I found the sticky U-joint and replaced it.

Anyway in the pic you can see that the U-joint would not flex as it should.

Note that the Guy that claimed that you can free up a sticking U-joint claimed that the sticking was due to dried up grease. But, there was some rust in the bearing caps on mine.
Attached Thumbnails
Thumping vibration from rear-u-joint-not-flexing-2019.jpg  
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  #15  
Old 04-12-2019, 11:10 PM
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Diesel 911......Thank you for the great info. The more I read and think about it, the more it is pointing to a bad u-joint or carrier bearing. On the drive home from work I was able to duplicate it, and the vibration feels like it is coming from like someone earlier said, between the seats and behind the center console. Geez, I hope I am not going to have to drop the drive shaft again, it was a PITA last time.....

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