ok,
I got the drive line out of the parts car, and was installing the better disks on it to put it in the running car.
There is a collar that is bolted on there, it fell off. Do I need it? if so does direction matter.
Thought I read that it was not needed, but do not remember, and can not find it.

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83 300SD Dark Silver Dark brown inside

http://www.peachparts.com/shopforum/attachment.php?attachmentid=49202&d=1194055732

If I did this right, this is the photo of the ring. this one calls it a balance ring?

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83 300SD Dark Silver Dark brown inside

The VAST majority of vibration issues are tire/wheel related. Next up is driveshaft.

Since you have a parts car with a good driveshaft it would be worth changing out. If you properly collapse the driveshaft you will not damage the flex disks unless they're rotten anyway. Surely between the two cars you can come up with a good set of flex disks.

Also, if it is driveshaft related, very often the problem is a notch worn in the universal joint. Loosen both carrier bearing mount bolts and get a washer or two. Remove one of the bolts all the way and put the washer between the carrier bearing mount and the body and then thread the bolt back in place and tighten both bolts. This will put the universal joint slightly away from the notch. It will often cure the problem. Using the word cure is probably not correct, it will MASK the problem.

One more thing. Remember that things like control arm bushings, track rod mounts, shocks and any other NON rotating part can not PRODUCE a vibration, but they can allow it to be transferred into the cabin. Rotating items produce vibrations.

If you have a parts car, do you have a known good wheel and tire? If so, put it on the car and drive it. If it doesn't fix the vibration move it to a different corner and so forth.

Hope this helps

Drive line did not fix this issue. I have all the wheels that were good on the parts car on this one.
Wheel bearings etc. seem ok.
It is not from the front, As I can feel it with the car in the air.
So.... felt the rear wheels, they seem tight like the front. Is that how to check the rear wheel bearings also?

I am about ready to just swap the whole rear sub frame... And now the truck is having issues..... ARRRGH!!!!!!!!!

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83 300SD Dark Silver Dark brown inside

As mentioned above, several times, the most likely culprit for random vibrations at discrete speeds are the tires. A mediocre tire will be out of round to the point where the driver will feel the condition at certain speeds when the vehicle frame is in resonance. Higher speeds might reduce the sensation.

The trick to find the runout of the tread is fairly simple. Jack up the vehicle and get a fixed object to stand in front of the wheel. Move the object close to the tire. A dial indicator is perfect, but you don't have to use one. Rotate the tire and observe the size of the gap that develops between the object and the tread. The gap will increase and then disappear with each revolution. If the gap is greater than .062", you'll certainly feel it when you drive. I've got a suspicion that your gap is .125" or so.

when you speak of run out, are you talking about up and down like a bounce, or in and out like a wobble?
I have changed all of the wheels and tires on this car, so if it is not a wheel then where next?
Also, since I do not feel it in the steering, does that mean it is on the rear? It is worse in the pass. seat than the drivers. About 20 and about 45

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83 300SD Dark Silver Dark brown inside

Explain in more detail, please.

What do you feel and how did you feel it..........??

Does it matter if the car is accelerating, coasting or decelerating?

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

it dies not matter if the car is accel or decel or coasting.
I have the car up on jack stands all the way around, so I got in and could still feel it.
Could it be the trans or rear diff? I do have some oil seeping from the rear diff. I have been keeping it full, but I do not know about the last owner.
It is worse when accelerating from a stop on a hard right turn. that feels different like the rear bushings are shot.

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83 300SD Dark Silver Dark brown inside

I have a 83 300D(160,000miles) with what sounds to be a similiar issue. The vibation is rotational in the 33mph to 40 mph range. Bought the car with 145,000 on it, and with the vibration. Been chasing the vibration for 15,000,,... I can put the car in neutral and cost down a hill and it will still vibrate in that speed range.

I have had two different sets of tires/wheels on it,.. took the drive shaft out of a parts car that I had been driving daily without issue. Put a new carrier bearing and isolation mount on the replacement drive shaft before installing(paying attention to the alignment marks when I took it apart and re-assembling) And have replaced the the trasmission mount.

When I had the drive shaft out, I inspected, rotated, tried to jiggle the transmission output shaft and the input shaft to the differential. Nothing seems to be out of the ordinary.

When I replaced the drive shaft I did not use new flex discs. I had ordered new ones,.. but I could find absolutely nothing wrong with old ones.

I am going to try and get the motor mounts changed this week-end.

Should the motor mounts be the culprit,.. and I'm not optimistic that they are,.. I'll be certain to post the good news.