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Discussion Starter · #1 ·
Hey!

I've had a sound from the drive shaft since I got on my 300 SE. Last week I changed the central bearing support, flex disc, motor mounts, transmission mount.
and now the car feels like new, shifts perfect and starts without any vibration at all. BUT I got into one problem, in low speed I have sound from the driveshaft and when I drive 80-100 I get vibration from the driveshaft which I didnt have before..

So I got under again, and noticed that the marks I did when I splited the driveshaft was not the same spline as the factory marks. So my question is, are the factory marks ALWAYS the right balance on these? I Tried connecting it with the factory marks, but the vibration was still there.

I got under again. again and again, until I finally changed back to the old central bearing support, and the vibration is now gone but i still have the wosh wosh sound as i started out with.

My conclusion is that with the new central support it gets alot stiffer, so I feel the vibration, with the old saggy one it still vibrate but I dont feel it anymore.


I did feel on the U joint, but I cant say if it is suppose to move like this? It has like a free play in the middle. Can this be the source of vibration?
Video: VID_20220618_085713167.mp4



Sorry for long text, I have read many treads but now im starting to loose it :D I hope someone has some suggestion.
 

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It has like a free play in the middle. Can this be the source of vibration?
I assume you're trying to show that it is "notchy", almost like it has a detent in the center. Yes. That u-joint is shot. It should move smoothly from one limit to the other.
 

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I was wondering, if is the U-joint, why with one bearing it vibrates and with the other one does not? The U-joint is the same in both cases, isn't it?

Although I am not excluding the U-joint, out of curiosity: how many miles on your car and what brand is the new bearing (and its bracket)?
 

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Discussion Starter · #7 ·
I was wondering, if is the U-joint, why with one bearing it vibrates and with the other one does not? The U-joint is the same in both cases, isn't it?

Although I am not excluding the U-joint, out of curiosity: how many miles on your car and what brand is the new bearing (and its bracket)?
Indeed good question, i have been scratching my head last week from that.
I think the vibration is there all the time but with the new bearing it gets a lot tighter and i then feel the vibration. The rubber on the old bearing is damaged so it vobbles more freely?

The new bearing with holder is Febi.
 

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Discussion Starter · #8 ·
Oh and the car is a 89 300se, with 270000 km.

Does anyone know if the factory mark always is the right balance on these? Im not sure why i doubt it but it wasn't aligned with those marks on my, and only one owner before me and only Mercedes who fixed things on this car before.
 

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Yes, the marks are supposed to line up. However, I also saw one shaft that did not have the two halves lined up perfectly from the factory, there was a difference of one spline. I knew the car did not have any vibration before, so upon reassembly I put it back the same way I found it, although it was one spline off. There were no problems afterwards either. Anyway, I attached the factory procedure for you.

With respect to the U-joint: I've seen that wear spot on shafts with much less mileage: 70k, 90k and 100k miles. All worked fine after reinstalling the shaft, the 70k and the 100k are my cars and no vibration up to 90 mph (did not go higher). However, I purchased the support bracket and its bearing from Mercedes dealership, no Febi parts or similar. That brings us to the core of your problem.

I suspect that the quality of the parts you installed may not have been appropriate. While I do not eliminate the U-joint from this equation, I suspect that your new middle bearing and its bracket may be your problem ( a W126 with ~ 168k miles normally does not require a U-joint replacement). Is up to you to decide what you want to do next: have the U-joint replaced by a specialized shop, or try one more new support bearing assembly but with parts purchased only from an authorized Mercedes dealer.
 

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Discussion Starter · #10 ·
Yes, the marks are supposed to line up. However, I also saw one shaft that did not have the two halves lined up perfectly from the factory, there was a difference of one spline. I knew the car did not have any vibration before, so upon reassembly I put it back the same way I found it, although it was one spline off. There were no problems afterwards either. Anyway, I attached the factory procedure for you.

With respect to the U-joint: I've seen that wear spot on shafts with much less mileage: 70k, 90k and 100k miles. All worked fine after reinstalling the shaft, the 70k and the 100k are my cars and no vibration up to 90 mph (did not go higher). However, I purchased the support bracket and its bearing from Mercedes dealership, no Febi parts or similar. That brings us to the core of your problem.

I suspect that the quality of the parts you installed may not have been appropriate. While I do not eliminate the U-joint from this equation, I suspect that your new middle bearing and its bracket may be your problem ( a W126 with ~ 168k miles normally does not require a U-joint replacement). Is up to you to decide what you want to do next: have the U-joint replaced by a specialized shop, or try one more new support bearing assembly but with parts purchased only from an authorized Mercedes dealer.

Hmm okey, this one was maybe half a turn / 5 splines off the marks..


I hear what you are saying. I think I will go with a new mercedes bearing, I can always take that one if I need to buy a used drive shaft later. Worth a try, after taking it down 5-6 times I do it pretty fast now ;) Thanks a lot for the input!
 

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Hmm okey, this one was maybe half a turn / 5 splines off the marks.
You should have said that up front. Half a turn is not right. I suspect that somebody got there before you did. I think if you do it again, taking your time, doing it by the book and using quality parts, you will be very happy with the result. Good luck.
 

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When a u-joint binds up like that you get two pulses for every rotation of the shaft. These pulses push the shaft sideways, out of line, in opposite directions. I'm guessing that the old bearing support is sloppy and doesn't transmit the pulses to the body as efficiently as the new one does. The solution is to replace the u-joint and eliminate the problem, not to try to cover it up. Unlikely a new carrier of different pedigree won't make much, if any, difference, and it will only get worse as the joint gets closer to failure.
 

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Nobody is trying to cover anything up here. There are plenty of cars like his that have twice that amount of mileage still on the original U-joint. Replacement of that U-joint requires a specialized shop, is not a job for him to do at home. Before he decides to go the road you are suggesting, everything else should be installed correctly and with quality parts.
 

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Hey!

I've had a sound from the drive shaft since I got on my 300 SE. Last week I changed the central bearing support, flex disc, motor mounts, transmission mount.
and now the car feels like new, shifts perfect and starts without any vibration at all. BUT I got into one problem, in low speed I have sound from the driveshaft and when I drive 80-100 I get vibration from the driveshaft which I didnt have before..

So I got under again, and noticed that the marks I did when I splited the driveshaft was not the same spline as the factory marks. So my question is, are the factory marks ALWAYS the right balance on these? I Tried connecting it with the factory marks, but the vibration was still there.

I got under again. again and again, until I finally changed back to the old central bearing support, and the vibration is now gone but i still have the wosh wosh sound as i started out with.

My conclusion is that with the new central support it gets alot stiffer, so I feel the vibration, with the old saggy one it still vibrate but I dont feel it anymore.


I did feel on the U joint, but I cant say if it is suppose to move like this? It has like a free play in the middle. Can this be the source of vibration?
Video: VID_20220618_085713167.mp4



Sorry for long text, I have read many treads but now im starting to loose it :D I hope someone has some suggestion.
I know where the vibration came from.)
 

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'17 GLS450, '14 GLK250 "Grandpa's Roadster" Project Car, 350SDL (Sold)
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Nobody is trying to cover anything up here.
I didn't mean to imply that. I said the worn out carrier is covering up the bad u-joint.

The u-joint is bad. Period. Nothing other than replacement is going to change that. Change the carrier and the bad u-joint will just hasten it's failure. Ultimately, the u-joint itself will fail and you'll have a loose driveshaft flailing around under the car.

TMSAISTI!

Too bad it didn't come with a grease fitting...
 

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Discussion Starter · #17 ·
You should have said that up front. Half a turn is not right. I suspect that somebody got there before you did. I think if you do it again, taking your time, doing it by the book and using quality parts, you will be very happy with the result. Good luck.
I did write that in the first post, "So I got under again, and noticed that the marks I did when I splited the driveshaft was not the same spline as the factory marks. So my question is, are the factory marks ALWAYS the right balance on these? I Tried connecting it with the factory marks, but the vibration was still there. "
 

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Discussion Starter · #19 ·
When a u-joint binds up like that you get two pulses for every rotation of the shaft. These pulses push the shaft sideways, out of line, in opposite directions. I'm guessing that the old bearing support is sloppy and doesn't transmit the pulses to the body as efficiently as the new one does. The solution is to replace the u-joint and eliminate the problem, not to try to cover it up. Unlikely a new carrier of different pedigree won't make much, if any, difference, and it will only get worse as the joint gets closer to failure.
Yea thats my guessing too! I ordered a new bearing support now from mercedes, I will try it and then transfer it to a new/old one when I get hold of one. I dont think I will pay 1k for a new driveshaft right now, but we will see whats happening.
 

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I did write that in the first post, "So I got under again, and noticed that the marks I did when I splited the driveshaft was not the same spline as the factory marks. So my question is, are the factory marks ALWAYS the right balance on these? I Tried connecting it with the factory marks, but the vibration was still there. "
Yes marka made for proper assembling drive shaft after repairs, this no need of balancing.
 
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