Hi All:
I am trying to diagnose a noise from under the car. I did search the threads but nothing exactly matched what I am experiencing so risking redundancy, I am looking for suggestions:

1985 300TD with 163,000 miles.

The noise is a regular clunking that speeds up/slows down according to road speed. It seems to be coming from the driveshaft area.

It does not occur on acceleration or significant deceleration, but is most noticible in a "coasting", or equal power (neither accelerating or decelerating) situation.

It goes away if I shift the tranny to neutral.

I put her up on stands and checked the following:

1. Flex Disks, look OK, no visible cracks or wear.
2. No discernable play in center bearing.
3. No discernable play in universal joint.
4. No slack in the CV joints.
5. I peeled back the seal and the splined area forward of the center bearing is clean and shiny.

The transmission shifts smmothly without any flare or noise.

Any thoughts out there?

I did notice from the service records that the PO mentioned this noise to a MB dealer at about 140K miles and the service note states
" Unable to locate the source of the noise. No need for concern at this time".

Boy, I am stumped. I guess I need to take her to a shop. Any suggestions as to a great vintage MD mechanic in the Morristown NJ area.

Thanks for all of your help!

Ron Young

What about the rear end? I had a problem with my 140 where it was making a humming noise, drove me nuts. After throwing several grand at it, I took it to a specialist at Park Place, he knew exactly what it was, it was a bearing on the rear. Sometimes when you have the weight and force off a car you can't feel the play, take a look at the transmission mount too. Also check the strut arms on the rear to the hub carrier, if you have worn bushing here that can cause funny noises. I would think that all the things that you checked are what any good MB tech would look at first, but if you can't find it, get a specialist.
Good luck!

__________________
Brian W. Heitman

www.MBCA.org/northtexas

Join MBCA!!!

Got the exact same problem on my 85 300TD. A rhythmic thumping that occurs only with the drivetrain unloaded. I had assumed it was the center bearing but haven't looked or replaced it. I'm glad you posted and that I didn't have the bearing replaced yet since now it doesn't seem to be the likely candidate.
I asked a similar question about it on the diesel discussion a few weeks ago. Someone suggested tires. Perhaps, but I don't understand why it can only be heard with drivetrain unloaded.
It doesn't sound like the rear end in mine.

Perhaps this is an oddity with the TD's.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Hi Kerry:
Dropped her off tonight at NV Coach & Motor works for a shot at diagnosing the noise. I will let you know what I learn.
Thanks, Ron

That doesn't sound like the name of a US business. Are you in the UK?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Hi Kerry, Yes, New Jersey USA. (NV is New Vernon).
Best Wishes, Ron

Here is the answer after a few days in a MB specialist shop. (They give a nice price break if you let them take thier time and do the work as time permits).
I stopped by today to see the progress and there were multiple noise sources.

1. The tie rod bushings for the rear stabilizer were gone, transmitted some noise to the chassis.

2. The big one, The right rear outboard wheel bearing was failing. This was the main culprit and caused the regular "Clunk" when the drivetrain was unloaded.

I can't wait to get my QUIET car back!

Total bill with Front End alignment will be about $400.00.

Best Wishes, Ron