Driveline bearing noise W123 ( driveshaft bearing, differential, etc ) ? - PeachParts Mercedes-Benz Forum

rkpatt · #1 07-24-2010, 09:31 AM

I am looking at a 1983 300D for sale. There is a constant driveline noise ( bearing noise rear center) . It very noticeable ( almost loud with the door open to listen ) . No changes on turns or with load . I will jack the car up and check the drive shaft for play and check the differential lubricant level . Will a worn or "dry" drive shaft bearing exhibit these symptoms before you can feel "play" in it ? - Thanks

Diesel911 · #2 07-24-2010, 12:01 PM

The Driveshaft Bearing is in a Rubber Mounting I donot think there is any way to gauge the end play because the mounting moves.

Safely Jack up both rear Wheels off of the Ground so they can spin and block up the front wheels so the car will not roll.
Put, the trans in a drive gear and let the wheels spin.
Listen around with a Mechanics Sthetoscope or someting like a long Screwdriver or my favorite a 3-4 foot piece of wooden Broom stick and see if you can locate where the sound is coming from.

Biodiesel300TD · #3 07-24-2010, 12:03 PM

Does the noise change with speed, or does it stay constant no matter the speed?

rkpatt · #4 07-25-2010, 01:09 PM

I tried the your suggestions using both stethoscope and broomstick checking the rear wheels and the differential . The noise seems to be coming from the front of the differential (pinion bearing ? ).

Quote:

Originally Posted by Diesel911

The Driveshaft Bearing is in a Rubber Mounting I donot think there is any way to gauge the end play because the mounting moves.

Safely Jack up both rear Wheels off of the Ground so they can spin and block up the front wheels so the car will not roll.
Put, the trans in a drive gear and let the wheels spin.
Listen around with a Mechanics Sthetoscope or someting like a long Screwdriver or my favorite a 3-4 foot piece of wooden Broom stick and see if you can locate where the sound is coming from.

To the the last poster - The noise gets louder with increase speed . I does not change noticeably with load .

Stretch · #5 07-25-2010, 03:11 PM

First thing I'd do is check the fluid level in the differential if you can...

rkpatt · #6 07-25-2010, 04:20 PM

It was somewhat low but not dry . I added more 90wt with no change after adding more .

dawsonj3 · #7 07-25-2010, 06:16 PM

My 83' has made a humming sound from the diff. since I've owned it (90 weight oil, diff is full). It's not the wheel bearings, as when I take my foot off the throttle, it stops making noise. I've replaced the center bearing, and the rear subframe mount. I still hear the sound on slower drives around town. Probably, the differential in the vehicle you are looking at is worn. These vehicles can go a long time with a worn diff - in fact most vehicles with more than 200K do have some noticeable diff. wear. My two cents as an owner of the same vehicle who has replaced almost everything underneath the car except the differential.

rkpatt · #8 07-31-2010, 06:11 PM

I plan on using the vehicle for lot of travelling so I really would prefer to repair or replace it . Most of the cars at Pull-a-Part have 250K+ miles too . It is tempting to try to rebuild it if the gear are good and the bearings are reasonably priced vs taking a gamble on the used ones from the Pull-a-Part . I guess that I need to read up here and elsewhere on rebuilding these . Recommendations are appreciated . - Thanks

Quote:

Originally Posted by dawsonj3

My 83' has made a humming sound from the diff. since I've owned it (90 weight oil, diff is full). It's not the wheel bearings, as when I take my foot off the throttle, it stops making noise. I've replaced the center bearing, and the rear subframe mount. I still hear the sound on slower drives around town. Probably, the differential in the vehicle you are looking at is worn. These vehicles can go a long time with a worn diff - in fact most vehicles with more than 200K do have some noticeable diff. wear. My two cents as an owner of the same vehicle who has replaced almost everything underneath the car except the differential.

farside · #9 09-07-2010, 11:07 PM

Have an 84 tdt with 237K and a noisy rear diff and it does bother me but so far so good. I'd like to know what kind of mileage does it take before a rebuild is in the cards...

Biodiesel300TD · #10 09-07-2010, 11:34 PM

Quote:

Originally Posted by farside

Have an 84 tdt with 237K and a noisy rear diff and it does bother me but so far so good. I'd like to know what kind of mileage does it take before a rebuild is in the cards...

It all depends on how it was taken care of. My 240D has the original diff, and has 307k miles on it.

JHZR2 · #11 06-26-2019, 12:14 PM

Quote:

Originally Posted by dawsonj3

My 83' has made a humming sound from the diff. since I've owned it (90 weight oil, diff is full). It's not the wheel bearings, as when I take my foot off the throttle, it stops making noise. I've replaced the center bearing, and the rear subframe mount. I still hear the sound on slower drives around town. Probably, the differential in the vehicle you are looking at is worn. These vehicles can go a long time with a worn diff - in fact most vehicles with more than 200K do have some noticeable diff. wear. My two cents as an owner of the same vehicle who has replaced almost everything underneath the car except the differential.

Figured I’d revive this thread as this is the phenomena I’m encountering too.

My 300CD runs smooth as silk, it’s incredible, until I get to about 40-45 mph. Above that it’s still smooth as can be, but I start to get an audible whining sound. Above say 65 road noise trumps it. The sound isn’t terribly loud but it’s not what one would normally hear.

The catch - let up off throttle and it goes away completely. Back to a nice smooth running engine and car. Add a little throttle and the noise comes back, still smooth as can be, just audible whine.

The other catch. My car sat for about 6 years without moving. So it could be something that’s reliant on motion (driveshaft support bearing?). Flex disks look perfect.

There is some clunk in the driveline when loading and unloading. More so than my 240d has. I’d think that could be trans, diff or the rubber mounting of the csb. Nothing obvious when looked at or up in the air rotating the wheels.

Suggestions?

Diseasel300 · #12 06-26-2019, 04:16 PM

Quote:

Originally Posted by JHZR2

Figured I’d revive this thread as this is the phenomena I’m encountering too.

My 300CD runs smooth as silk, it’s incredible, until I get to about 40-45 mph. Above that it’s still smooth as can be, but I start to get an audible whining sound. Above say 65 road noise trumps it. The sound isn’t terribly loud but it’s not what one would normally hear.

The catch - let up off throttle and it goes away completely. Back to a nice smooth running engine and car. Add a little throttle and the noise comes back, still smooth as can be, just audible whine.

The other catch. My car sat for about 6 years without moving. So it could be something that’s reliant on motion (driveshaft support bearing?). Flex disks look perfect.

There is some clunk in the driveline when loading and unloading. More so than my 240d has. I’d think that could be trans, diff or the rubber mounting of the csb. Nothing obvious when looked at or up in the air rotating the wheels.

Suggestions?

The center support bearing is unlikely to be the source of noise since it goes away when you let off the accelerator. Since the center bearing is not loaded it should not change any noise it makes as you go from accelerating to coasting.

You could certainly have a bearing in the U-joint going bad on you. My SDL had that issue, it would develop a vibration around 45-50mph that would reach its peak around 65-70mph. My car sat for 10 years in a field and the U-joint was definitely stiff and notch compared to the rebuilt driveshaft I installed on the car.

The rear end could be causing some of your slop, however I'd expect a growling noise, not a whine if it were worn to the point of being an issue. The SDL had a worn diff too that resulted in a bit of driveline slop, but other than clunks when changing directions or abruptly downshifting, it never transmitted any noise to the cabin.

JHZR2 · #13 06-26-2019, 07:11 PM

I’ve isolated the sound to only between 40-50 mph. Sounds like the diff. Cruising only - accelerate and the sound goes away; get off throttle and it goes away...

m5mulli · #14 07-23-2020, 07:24 PM

I am having drive train noise as well.

With mine its only on deceleration. Give it just the smallest amount of throttle and the noise is gone. Turning has no effect. I changed the diff fluid. It was old and low. It made absolutely no difference.

Its not a whine or a click or a thump. More of a gear growing noise.