Might have found the vibration
 

After nearly 2 years of ownership and almost as many trying to sort out the driveline vibration that has plagued my 81, I finally took it to my Indy
who drove it and eventually felt the vibe. He put it on the lift and after a short inspection found a blown transmission mount! He said that it might be the cause of the vibe since it changed the driveline alignment and could telegraph engine vibes to the rear.
The motor mounts felt ok.
I got a new T-mount today and will report back once installed and tested.
Does this car 81 240d only have the two motor mounts, engine shock and trans mount or is there another mount?

Yup, 2 engine mounts, 1 trans mount, and engine shocks are variable. Some have no engine shocks, some have one, and others have two. So I'd looks and see what yours has for engine shocks and match what you've got.

The transmission mount is different for manuals and automatics. Get the correct one:

Left = manual, right = automatic

http://farm4.static.flickr.com/3465/...20d056c0_z.jpg

I got the correct manual one.

I have not seen any engine shocks on the manual 240Ds.

Don't worry about the engine shocks. I'm pretty sure I destroyed mine jacking my engine up. I've noticed no difference in driving or shutdown.

However I did replace the motor mounts, trans mount, differential mount, and the rack dampener. Car feels awesome no vibrations at all.

My vehicle coasts a lot better now. Why I don't know, but I'm guessing the trans mount has some job in dampening the vibrations of the engine.

My old one felt soft and smooched easily. New one was rather hard in comparison.

Replacing it was way to easy. Probably 30 minutes at best.

I have 1 engine shock that I replaced last year

On my 83 240 there was a tab mount that came off the front of the crossmember and fitted into a rubber lined slot in the back of the dropped sump oil pan.

Not!
 

:confused: The new trans mount is in but alas the vibration remains.
I am more convinced than before that it is somewhere in the rear end of the car.
We checked the lubricant in the axle cans and it is still there and fluid.
The diff lube is fresh,
Minimal rotary play in the driveshaft.
Wheel bearings are ok but not perfect. A little movement in the right rear wheel but not excessive.
flex discs ok
new center carrier and bearing.
Any other input here this is really frustrating:mad:

If you can "feel" movement on the right rear wheel I think you might want to measure it.

It should be 0.04-0.06 mm

See

http://www.peachparts.com/Wikka/W123RearWheelBearings

I spent $500 (parts only, I do my own work) replacing axles, wheel bearings, ball joints and completely disassembling and reassembling the brakes on my TDI Jetta chasing a vibe. It turned out to be an out-of-balance wheel. I had the wheels rebalanced initially but it wasn't done properly and the symptom remained.

Start with the cheap stuff and work your way up.

FWIW, I put CVJ axles on my 300D and it cleared up a bunch of vibes both driving and idling in gear. One was so shot that it was binding up. How are your axles?

Huh, an "auto trans" 240D I had once had one engine shock, didn't know the manual cars had them, non of mine have had them. I remember on the "Auto car" trying to figure out how to hold the shaft and turn the nut when pulling the engine:o

I had vibe before I replaced both the wheels and tires.
The axles are original, they aren't binding, the boots are uncracked and when my Indy snipped off the clamp on an inner boot, a drizzle of oil started to leak out so we know there is still lube in there and he added some light grease to the outers just for kicks.

A possibility is the driveshaft center U-joint is seized & binding. Unfortunately, those are staked in place and not normally replaceable without buying a new shaft-section.
However, there are driveshaft shops that can cut & weld in a new driveshaft end with a replaceable/greasable U-joint.

Happy Motoring, Mark

DS ujoint is a little "notchy" but not seized or clunking