W108 Vibration - PeachParts Mercedes-Benz Forum

Baxterdown · #1 07-12-2014, 09:51 AM

Hi guys,

My 1972 280SE 4.5 has a vibration (it came with it when I bought it a few weeks ago). I thought it was the tires that were out of balance but it wasn't that (at least not that alone). The vibration feels like it's coming from the center of the car and its pretty apparent. It increases in speed and strength as I accelerate. The mechanic thinks it might be the engine mounts.

Has anyone had any experience with something like this?

craftysince86 · #2 07-12-2014, 09:59 AM

Does it ease at certain speeds? Or the faster you go the worst it gets and never plateaus?

JMela · #3 07-12-2014, 10:21 AM

Do a search using the term "flex disc". That's a common one.

Idle · #4 07-12-2014, 03:20 PM

Check your carrier bearing. Some cars have them and some don't depending on the engine and wheelbase.

The driveshaft is normally a two piece thing that is joined in the middle and suspended from the center by the carrier bearing which is actually two parts: The bearing and the carrier. Both are cheap and easy to replace if you have a lot of time since sometimes it helps to remove the exhaust system to take out the driveshaft.

)Some 115's have a three piece driveshaft with two carrier bearings, but I have never seen a three piece on a 108.)

And while you are in there you might as well replace the flex-disc if your car has them. Some 108's and 109's have U-joints and their replacement is an adventure in itself. Those are best left to a professional and information on that can be found at the M-100 site since the 6.3 owner all need to deal with this. (The International M-100 Group)

Be careful if you do need to remove the driveshaft. They are balanced at the factory as a unit so mark them with some white paint so you can put the two parts back in the same way they came out. And be careful not to knock off the square pieces of metal that are tack welded to the driveshaft as those are the balancing weights. If you do knock them off you can put them back on with superglue. At least that's the way I have always done it.

To test the carrier.... First jack up the car and find the middle of the drive shaft. It will run through a brace looking thing that is bolted to the underside of the car. See if the shaft will move up and down in the carrier. If so the carrier is shot and that is what is making your noise. The driveshaft is rumbling around inside the carrier as it turns. The bearing itself might still be good but they are cheap and easy to replace once you have the driveshaft out.

Baxterdown · #5 07-12-2014, 05:03 PM

HOLY CRAP!

There are some "flex disc" horror stories out there! Is it not safe to drive my car?

craftysince86: the faster I go, the more prominent it gets. Odly enough, on some roads it's almost unnoticeable at speeds of 15-30MPH.

Idle: my engine is 4.5, standard wheelbase (72 280SE 4.5)

twinockchef · #6 07-12-2014, 06:05 PM

The flex disk and the drive shaft mount are right under the front seats.
Considering the age it is always wise to check the condition of the subframe and engine mounts. I would not be surprised if they have never been replaced. If you do replace them use OEM Mercedes parts. After market rubber parts are good and cheap for some things but they normally do not hold up over time. The OEM parts are of a better quality.

Idle · #7 07-13-2014, 06:13 PM

There is nothing to be scared about, but it is best not to let this go. It will just get worse. At this stage it is nothing more than a routine repair.

Graham · #8 07-13-2014, 07:54 PM

Quote:

Originally Posted by Idle

Check your carrier bearing. Some cars have them and some don't depending on the engine and wheelbase.

I would second that.

Centre shaft carrier bearing on my W123 was worst at about 50-60mph. The car body would "roar" when it got to a certain speed. Some sort of harmonic vibration.

I don't know how difficult it is to get at the bearing to inspect it on a W108. On my R107, that area is covered. But there is a hole in cover just behind the transmission. I used a small digital camera and took some blind pics looking back down the tunnel. You should see something like the pics below, even although they are from different MB. If the bearing is damaged, you should be able to see it. While in there, have a look at the flex disks at both ends because as has already been said, they cam make a noise, They can also causes serious damage if they let go:

New bearing
https://www.dropbox.com/s/edz3bzavxcog1fn/new%20hanger%20bearing.jpg

Looking down tunnel:
https://www.dropbox.com/s/tghm3151dtpycz7/Midshaft%20bearing.jpg

Flex disk with crack:
https://www.dropbox.com/s/4o3j6hx2niygtml/Flex%20disk%20crack.jpg

Baxterdown · #9 07-13-2014, 08:49 PM

Thanks Graham! WOW! Great info! -- my car is in PARKED until I can get it to the mechanic in the next couple of weeks (I don't want to risk my safety or major damage to the car).

Thanks again,

Jose

Baxterdown · #10 08-08-2014, 04:28 PM

UPDATE:

I took the car to the mechanic today and he put it up on the lift. The flex disc is intact. The bottom screw is "pushed forward" a few millimeters, but the disk itself looks good.

The mechanic moved the drive-shaft with his hand and immediately noticed that it was moving too easily. After further examination he found the drive-shaft sender support to be bad.

He said that he still has to take the whole thing apart so he'll give it a thorough look but that the problem is not as serious as we (you guys and I) originally thought.

I'm still gonna keep driving the car to a minimum until I can get it fixed in the next couple of weeks.

Baxterdown · #11 08-08-2014, 06:21 PM

I ran back to storage and took a quick pic of the flex disc. I couldn't get under the car far enough to shoot the sender support. Will try tomorrow. ITMT here's the disc:

Baxterdown · #12 09-06-2014, 08:24 AM

Hey guys,

I was finally able to have the vibration repaired. They replaced the driveshaft center support unit, the flex disc (which was ok, but I had it done as preventive measure), and the u-joint, which turned out was bad.

The car now drives amazingly smooth with the exception of 30-40 MPH where it has a different kind of vibration. This one I can feel through the steering wheel and accelerator pedal.

I did some research and found this post where another member had the same symptoms after replacing the u-joint.

Does this mean I have to get the driveshaft rebalanced? Should the mechanic have done that as part of the repair job?

Jose

Jub · #13 09-06-2014, 11:21 AM

Could be the tie rods (inner and outer); or the drag link.

If you raise the car up and wiggle your tires there shouldn't be any movement.

In the pic attached, you can see the left rod (and on each end there is an inner and outer tie rod; sometimes these need replacing).

Hope this helps

Jub · #14 09-06-2014, 11:53 AM

Heres a pic of all three (one rod on left; one on right; and one in center).

Each rod has ties on each end (total of six). Anyone of these tie rods can have play and cause wiggle at certain speeds.