New Flex disks - now it vibrates!
 

Have not seen this written about before:

1990 300E. I replaced the front and rear flex disks. Did not replaced bearing or carrier as I could detect no play there.

Symptom before were clunking due to mucho play in front disk. Rear disk was OK but I replaced it anyway, since I was there.

Had no vibration before, just clunking.

Now, no clunking but I have a vibration.

In the morning, when the car is cold, there is a very obvious driveline vibration from 35mph up. Only when coasting or light throttle. As the car warms up it fades away and stays away as long as the car does not cool completely off again.

???

Thanks

Was the driveshaft separated during the replacement of the flex disc?

No. I did not take the driveshaft completely out and did not separate it.

Also, I installed the flex disks with the writing toward the shaft, like the originals were.

And, I properly placed the two different length bolts in the front flex disk.

Thanks

i had the exact problem with my 1990 190E. How did I get rid of the vibration? I sold it! Sorry.
Good Luck, I never did figure it out.

Driveshaft nut too tight
 

I guess you had to collapse the driveshaft to get the flex discs out? To do so, you probably loosened the big (48mm?) nut in the middle of the shaft where the front and rear halves meet.
The manual calls for 30-40Nm when re-tightening this nut. That is very little considering the size of the nut. Actually, this is on purpose as the driveshaft needs to adjust slightly in length to relieve stress. When the nut is too tight, stress may cause vibrations.
Bruno

Well, I did not touch the big nut at all. The front shaft slid back just enough with the nut as is.

Thanks

Vibration
 

Check your motor mounts and transmission mount.

John Mlynick
92 190E 2.3 140,000mi

Motor/Tranny mount sounds probable, wouldn't the vibration be present all the time if it was the drive shaft?

Any ideas on how to tighten the big 49mm nut to the torque spec without the ability to get a torque wrench on it? I have two or three torque wrenches, but I can only put sockets on them and a socket will not fit on the nut with the two halves of the shaft in place and I do not have a crawfoot adapter in the 48mm size or even know if one that size exists.
How can I torque it to specs?

It is an essential characteristic of oscillations/vibrations that a very small amount of initial vibrational energy 'feeds' on surrounding energy, channeling it into the vibration mode. Often, a very small correction is all that is needed to eliminate a strong vibration. In your case, NOT replacing the center carrier is the clue I would follow. Likely, even if you notice little play, the support has deteriorated, allowing just enough movement to amplify small power-line vibrations. Cruising above 35 mph requires enough power from the engine to feed the vibration if there is any weakness in the driveline support.

Steve

When you say "..writing to shaft, like the originals.." IF you see any writing that says
"VORNE" that side mounts to the front. There is a chance someone got one of the old ones backward. Other than that, uuhhh... what everybody else said.

For the nut, big crescent or one like it, fish scale, little thread lock on the threads, helper or two to hold the shaft... I helped a friend with his like that a couple years ago - so far so good.

For the first three days after I replaced the disks, I would get the vibration just as described, exactly the same every morning, until things warmed up.

This morning I backed out of the garage and headed down the road. This time there was NO vibration.

So, either it was sitting in the "right" position overnight and will vibrate tomorrow, or it has healed.

You have to leave the center bearing bracket mounting bolts, rear trans mount bolt, and drive shaft slide nuts loose and push the car foward/backwards a few times for the drive assem to center/align itself..
...then you tighten everything up.

Sorry to hear about your vibration, mine was the center support. If ya spent the money on the flex, change the center support. It's only 30.00 and the labor. Read my write up it will help.

Where is the write up? DIY?

Bad motor mounts cause the car to clunk when your dirve it.....

I would look at the other parts of the drive shaft including mounts, bearings. Have you looked at your differential?

Hi Brewtoo,
I had a really bad vibration on my '75 280 that was most noticeable around 35mph, and it turned out to be the plastic bushing that the driveshaft front centering pin goes into, and that keeps the driveshaft centered - it was worn out and didn't keep the driveshaft aligned. Replacing it wasn't too hard, and it was very cheap to buy. (The driveshaft sort of "plugs" into the rear of the transmission as it fits up to the flex disk, and the plastic bushing is what holds the shaft centered - the one on my '75 was goose-egged from wear)

If it weren't for bad luck...
 

Yesterday, I did this entire job over again. This time, rather than leave the driveshaft in and replace the flex disks front and rear, I removed it entirely and replaced the center bearing and carrier. BTW, all of this is not a hard job but it is intimidating if you've not done it before. It does take some time.

Anyway, I removed the old bearing and carrier (which looked and felt fine). I did the trick of heating up the new bearing to about 200' and plop! it fell right into place on the shaft.

People say that the big 43mm nut is usually not very tight. Mine was tight. I had to hit the wrench with a hammer to get it loose.

I also replaced the trans mount, which had sagged a bit.

I put it all back together and drove it. No vibration! Until......

This morning the temp was in the 50s. I got in the car and headed down the street and Dang! the vibration was back starting @ 35mph.

It is temperature related and load related. Cool temps and no/low load is when it vibrates.

I notice that the trans mount crossmember has slotted holes so that it can be adjusted from side to side. It sits all the way to one side. Evidently came from the factory that way. I wonder if it should be more centered?

The driveshaft sections came with the factory alignment marks. However, they were not lined up exactly...probably 15 degrees off. I think it came this way from the factory. I doubt 15 degrees would make a big difference. I put it back together the way it had been for the last 16 years.

And the u-joint. Should I feel any detent in it? It has a mild detent in both directions that will stop it and hold it exactly straight. Is that normal?

And the centering sleeves have no noticeable play.

Hi Brewtoo,

That U-joint should be perfectly smooth, ie NO detents... the detents most likely mean that there's a little wear that's causing the "notching" effect. I think you better plan on replacing the U-joint.

Yes...the u-joint has roller bearings and a cross shaft.. x/y movement should be perfectly smooth. When there is notching, one of the rollers has worn a slot/notch into the cross surface and the notching you feel is the rollers popping in/out of the wear notch..probably more than one.
Time for a joint ..:)
Get one with the greazzzze fitting if you can find it.