Flex disc / center support replacement, now resonance.

[ascalise]

I changed the flex discs and center support today on my buddies 85 300sd. It had a bad vibration under load but was smooth as silk and silent other than that. I got it back together and the vibration is gone 100% but now I have this strange resonance at 1,000 rpm and again at 2,000 rpm. It does it sitting still or moving. It feels as if the exhaust is making contact with the body but it isn't. Anyone experienced this? I have to figure it out. The car is noisy and rough now.

[C Sean Watts]

Originally Posted by ascalise

I changed the flex discs and center support today on my buddies 85 300sd. It had a bad vibration under load but was smooth as silk and silent other than that. I got it back together and the vibration is gone 100% but now I have this strange resonance at 1,000 rpm and again at 2,000 rpm. It does it sitting still or moving. It feels as if the exhaust is making contact with the body but it isn't. Anyone experienced this? I have to figure it out. The car is noisy and rough now.

Did you line up the index marks correctly on the two shaft halves?

[ascalise]

I sure did. I marked everything that came apart and put it back together the same way. I don't see what this has to do with the problem though since it does it sitting still in park or neutral.

[Diesel911]

I recently read in one of the forums that you snug up but do not tighten that Drive Shaft Coupling Nut (46 or 47mm) put the Car back down on the Wheels and roll the Car Back and forth to settle the drive shaft in the Coupling and then tighten it up.

I cannot recall if it had to be in gear or not but the Member said the proceedure was in the W115 Manual.

But, you said it resonates when is not moving.

[ascalise]

Ok, I took it back apart real quick. It was the center support. I loosened it and rolled back and forth a few times again and now its gone. I took it down the road for the first time 60mph+ and it has a really bad high frequency vibration that was not there before. Man when it rains it pours. It is barely noticeable around 40mph then comes on hard at 60+

[Diesel911]

Originally Posted by ascalise

Ok, I took it back apart real quick. It was the center support. I loosened it and rolled back and forth a few times again and now its gone. I took it down the road for the first time 60mph+ and it has a really bad high frequency vibration that was not there before. Man when it rains it pours. It is barely noticeable around 40mph then comes on hard at 60+

Your thread is scaring me.
I am changing the Support Mount and the Support Bearing and also am 1/2 way through removing the U-joint on the Drive Shaft before I finish removingthe U-joint.
I am waiting to see if the U-joint I ordered is going to be the correct one.

After I get the above sorted out I do not know if I will end up with some issue like you are having.

[ascalise]

How are you changing the U-Joint? It normally isn't serviceable by a DIYer.

[Stretch]

Folks don't forget to adjust the rear engine mount after correctly fitting your propshafts!

[ascalise]

Realized I posted in the wrong thread just now.

OK, took everything back and put the new transmission mount in a little while ago. Resonance is not as bad and it moved up to about 70mph from 55-60mph at its worst then clears up after that.

[Diesel911]

Originally Posted by ascalise

How are you changing the U-Joint? It normally isn't serviceable by a DIYer.

See post #31
My U-joint Repair thread
http://www.peachparts.com/shopforum/showthread.php?t=293976&page=3