300SD rear tapping/clack sound at 10-35MPh
 

Hello all,

Just removed the back seat of my 84 300SD to use the additional space to carry some stuff. At any rate while traveling in this condition noticed a tapping/clack type of noise coming from the rear of the car, it really is noticeable while going uphill or giving lots of fuel during take off. It is most pronounced at 10 and 30 MPh. Could the pumpkin, 1/2 shafts, rear wheel bearings be making said noise? At first I thought it could be U joints, but MB does not use "conventional US" U joint concept.......
Any help is greatly apreciated.
Adriano:confused:

Does it sound like this?
 

Hello and thanks for the response.
No it does not sound like that, but you gave ma an idea to record the sound and then post it. What forum group did you post too?
Also let me know what your mechanic found on your particular noise.

Adriano

Is it like a THUNK THUNK THUNK?

I have the same thing at about 25 MPH, especially if I am turning to the left. I believe it is a CV joint. Whenever I turn a direction to put more weight on it it thunks even more.

Crawl under the car and check your center drive shaft bearing/mount and the flex discs. Make sure there is very little play in the center mount. Grab the shaft and try to move it up and down(toward the ground and roof of the car). If there is no slop the center mount.

The other thing you might do is have someone sit in the rear and listen carefully for exactly where the noise is comming from. It might eliminate some possibilities.

Does it do it over bumps only or all the time during that speed range? If it's over bumps its the sway bar links.

Check your rear sway bar end links:http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2490TUBYH2510M6E7Z&year=1984&make=MB&model=300-SD-002&category=L&part=Sway+Bar+Link

Put the rear seat back in and turn up the radio :rolleyes:....seriously hop underneath and start checking for worn, loose, damaged, parts. Maybe put up on jack stands....sturdy stands....have a good friend run it through the gears while under and looking....could be dangerous if not a good friend. :behead:

Hello guy's,

Thanks for all the wonderful suggestions (even the funny ones).

I believe Biodisel300D may have some good points. Due to work schedule have not been able to take more looks at this, but I just noticed that at around 60MPH I also get an intermittent vibration, very similar to tire out of balance condition and since it feel more under my rear (not car rear-end ;-)) it would point toward the rear of the car.
In short as soon as I can will check the drive shaft bearing play and look toward the differential, axles and rear bearing.
BTW how susceptible are the 300SD differentials to develop "issues" that show up under power take offs? Bear in mind my baby has over 500K and owes me absolutely nothing but my care and appreciation.

Adriano

Well just in case someone might stumble on this post with a similar situation, I 'll post a very late discovery of the culprit.

Turned out to be the plastic rear sway bar connectors. Lack of lubrication in the knuckle joint was making the clacking sound. Just by sheer coincidence I happen during the rainy season had a washout on my long downhill driveway (a 12" 20' rut was created) one sat morning going out the left rear in the gully the right above I heard a 'pop' stopped to check things out no sign of anything out of place or broken, continued on. Upon making a left sharp turn around 20mph a scraping sound now was audible along the clack. Inspection for the scraping resulted in discovering the left rear connector being broken.
Replaced both linkage connectors and gone was the clack and the new scrape :)

Thanks to all who suggested input.

A.

Post #6.;)