Strong vibration during acceleration - Page 3 - Mercedes-Benz Forum
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post #21 of 33 (permalink) Old 12-11-2018, 01:42 PM Thread Starter
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Originally Posted by okyoureabeast View Post
Your 450sl might be different than my car.

On my 84 380sl, the idiot PO had a shop make the entire exhaust system on giant long pipe from the passenger side header all the way to the rear. Where there should be connectors that bolt together, it looks like someone welded the piece in place. I don't know if that's OEM or not.

The aftermarket exhaust pieces that i've seen all bolt in sections which would make this job a lot easier to do.

From what MBGraham said, you might be in the same situation as me. The only way to know is to crawl under and check.

Don't be intimidated by this job. Like I said, the exhaust is a b!tch to remove, but once you do it you can easily put copper anti seize onto the bolts which will make removal easier. I recommend putting the front of the car on ramps and jacking the rear up on jack stands. This will give you the clearance you need to do the job.
Good idea on using ramps for the front...I was using jack stands in the front and in the rear....spooky!
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post #22 of 33 (permalink) Old 12-11-2018, 03:12 PM
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Originally Posted by Mercy107 View Post
Finally found time to get the car off the ground and get underneath it. Thank you for the replies, you folks helped me to the next step. I think I know the answer but check the photos and video below and let me know what you think.

First, I tested the engine mounts per roncallo. I had my wife put the car in drive / reverse with the brake down and gave it gas both directions. The engine had absolutely zero movement. You could not see it move no matter how much gas she gave it. Solid engine mounts. The motor was removed and rebuilt by Herndon Mercedes in Fresno in 2009..so I believe the engine mounts are fresh.

However, the flex disks are not so great, and I question the center bearing. The trans mount look intact but may as well replace it too. Check out the photos and really watch the video and let me know what you think. I really appreciate everyone's help on here, I had no idea where to start. I tried to put the photos in order. The first photos are of the front flex disk, then the center bearing and the last photo is of the rear flex disk. Oh, and I had 4 jack stands, wood blocks, and a 4 ton jack all supporting the car.....every few minutes I would imagine how it would be if the car crushed me..ha! No matter how much support, its still spooky laying underneath this heavy beast.

https://www.youtube.com/watch?v=7N6A...ature=youtu.be
Flex disks are definitely bad. I cant tell if its the angle or not but the center bearing does look to be sagging. Transmission mount I cant tell but the rubber may be compromised by the oil.
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post #23 of 33 (permalink) Old 12-11-2018, 03:18 PM
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Originally Posted by Mercy107 View Post
Anyone have an opinion on the center bearing and transmission mount? Does the center bearing look normal? Is the play shown in the video normal? Does the transmission mount look ok? I would love the issue to only be the flex discs since I won't need to remove the shaft, but if the bearing needs to be replaced then I must do it. Let me know what you folks think.
That's not play your seeing that is the diaphragm moving. That's fine. But it appears from the pictures not to be on center. In any case since your flex disks are shot you might as well remove the drive shaft for a good inspection. And as usual happens well since you have it out and it probably is old just replace it.
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post #24 of 33 (permalink) Old 12-11-2018, 09:01 PM
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Originally Posted by Franklyspeaking View Post
I am no expert on the R107, but this drive arrangement is very similar to the W123. I don't see anything in your pictures and videos that looks bad enough to cause your problem. The center bearing runs through a flexible rubber donut, which looks in tact. I had seen flex disks that had reinforcement fiber coming loose that had no vibration.

Have you looked at the CV joints and axle shafts? That is another component that can cause vibration under load. Most of the time this is caused by lack of lubrication. The rubber bellows can deteriorate and loose the lubricant. In my W123 they used a gear oil type lubricant and when the rubber bellows goes, so does the oil.

Good luck - Hope you find the problem.
I do agree with Jerry. There is nothing in those pictures that would cause Strong vibration. Those cracks you see in the flex dist will cause vibration which you can feel but not at a level that I would characterize as strong.
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post #25 of 33 (permalink) Old 12-12-2018, 06:43 AM Thread Starter
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Originally Posted by roncallo View Post
I do agree with Jerry. There is nothing in those pictures that would cause Strong vibration. Those cracks you see in the flex dist will cause vibration which you can feel but not at a level that I would characterize as strong.
Thanks for the advice. What my be 'strong' to me may not be that strong of a vibration to others. I tend to obsess and listen too hard at times about every sound this car makes. I will try to explain it better:

From a stop light, if I accelerate at an easier pace, keeping with the rest of the pack, I would say the vibration is slightly moderate. I can accelerate without any vibration if I am very soft on the pedal. But if I hit the gas firmly (half way to the floor?), with the goal of putting several car lengths in between me and the car behind me as quickly as possible, the vibration is strong. Also, it doesn't start to vibrate until I am at about the 35 mph mark. I would think bad CV joints / half shafts would have other symptoms other than vibrations if they were bad. I could be wrong. I have read that clicking / clunking at nearly all speeds will be heard in bad half shafts / cv's. Also, with the boots being intact and pliable, I would assume they are greased up as they should be.

I am going to go ahead and replace the flex discs, center bearing, trans mount, possibly diff mounts over my Holiday vacation towards the end of this month. Will also be replacing the steering coupler and damper, who has time to relax on vacation anyway! I will report back then. Hopefully the vibration is gone. Thanks for everyone's tips and advice.
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post #26 of 33 (permalink) Old 12-12-2018, 08:39 PM
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Originally Posted by Mercy107 View Post
Thanks for the advice. What my be 'strong' to me may not be that strong of a vibration to others. I tend to obsess and listen too hard at times about every sound this car makes. I will try to explain it better:

From a stop light, if I accelerate at an easier pace, keeping with the rest of the pack, I would say the vibration is slightly moderate. I can accelerate without any vibration if I am very soft on the pedal. But if I hit the gas firmly (half way to the floor?), with the goal of putting several car lengths in between me and the car behind me as quickly as possible, the vibration is strong. Also, it doesn't start to vibrate until I am at about the 35 mph mark. I would think bad CV joints / half shafts would have other symptoms other than vibrations if they were bad. I could be wrong. I have read that clicking / clunking at nearly all speeds will be heard in bad half shafts / cv's. Also, with the boots being intact and pliable, I would assume they are greased up as they should be.

I am going to go ahead and replace the flex discs, center bearing, trans mount, possibly diff mounts over my Holiday vacation towards the end of this month. Will also be replacing the steering coupler and damper, who has time to relax on vacation anyway! I will report back then. Hopefully the vibration is gone. Thanks for everyone's tips and advice.
When my flex disks had cracks just like the ones in your picture I would notice a vibration that came on at about 30 MPH. I replaced only the flex disks at the time and its been good for about 10 years now. The rest of the drive shaft I had done earlier.
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post #27 of 33 (permalink) Old 12-14-2018, 05:21 AM
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Originally Posted by Mercy107 View Post
Anyone have an opinion on the center bearing and transmission mount? Does the center bearing look normal? Is the play shown in the video normal? Does the transmission mount look ok? I would love the issue to only be the flex discs since I won't need to remove the shaft, but if the bearing needs to be replaced then I must do it. Let me know what you folks think.
My opinion on all things rubber is....if the car is OLD and you have no idea about the life of said parts....then start changing them.

This is called preventative maintenance.

After it is done...you will have a benchmark for these parts.

AND....it will probably solve any vibration issues.

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post #28 of 33 (permalink) Old 12-14-2018, 06:44 PM
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Originally Posted by MBGraham View Post
Your 73 is probably same as my 72, but I can't get at it right now to have a look.

Not sure if you could lower exhaust a bit. Or just remove the rear part that may be in the way? When I had work done on transmission leak, the shop took the complete exhaust off in one piece. Saw them re-install it and recall them having some difficulty - the bolts at the exhaust to manifold joint are hard to get at and likely hard to undo. If I remember correctly, car was on hoist and they had long extensions and an impact driver. Exhaust shop put in new seals later(some sort of soft metal) when I had them install a boss for my wideband O2 sensor. If those front joints can be avoided it may make job easier.


I saw this trick on a post somewhere in Benzworld. If you weld a nut onto the exhaust-to-manifold bolts, they won't need an awkward wrench to keep them from spinning next time they are loosened or tightened...





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post #29 of 33 (permalink) Old 12-16-2018, 07:57 PM
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I had the same problem years ago. Changing the transmission mount cured it.
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post #30 of 33 (permalink) Old 03-27-2019, 08:20 AM Thread Starter
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Post-repair update for those researching similar driveline vibration issues;

I ended up taking the car to a really good Indy who only works on older Merc's.

The main source of the vibration ended up being the transmission mount and the driveshaft Centering sleeve / bushing. The transmission mount was not only very soft (almost gooey), it was the wrong mount. The mount was for a different year model and the PO had used spacers to make it "work". The rubber in the driveshaft centering sleeves were nearly gone as well. Those were the two main culprits. The center bearing was ok and the flex discs only had very few small hairline cracks showing up.

In the end, I had the new transmission mount installed, new flex discs, new center support and bearing, differential mount (soft as well), and host of odds and ends replaced. The rear-end was whining so I had it replaced while everything was apart. New steering coupler, rebuilt steering box, and rebuilt the power steering pump and added new power steering hoses. Now she silently glides down the road like driving on glass. Its glorious....although my bank account is still smoldering.
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