I have noticed a high pitched sound like a hair dryer in the trunk in the 85 SD lately. I believe it may be a wheel bearing on the left side, seems louder on the drivers side when I listen with the windows down.

I'm wondering if the bearing noise will go away when I check it unloaded, lifted off the ground???

It could also be the driveshaft carrier bearing. But I would start off by changing out the diff fluid with synthetic or use staight 90w or higher to see if it will go away. If not then you need find a way to get down there and hear where the noise is located.


It might go away but be sure to properly support the vehicle if you're going to attempt it.

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1983 123.133 California
- GreaseCar Veg System

I am interested in this as well and have posted previously on the subject. My 85 300SD continues to make a loud noise that seems to be coming from the passenger side rear. Have changed the diff oil too. I have had the vehicle on jackstands and running and cannot duplicate the noise. The noise is present regardless of pressing on the pedal or coasting. I also seem to have some driveline noise around the center of the car but thats a different subject. Also something of note, when the car was on jackstands, speedo aproaching 30mph, the rpms and speed increase dramatically. Is that the turbo kicking in?

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1985 Mercedes Benz 300SD, TMU
2015 Chrysler 200S

This seems like a very common problem with these cars. I've had the same problem with whine since I bought mine. I've changed to synthetic gear lube and I've checked the wheel bearings, etc. It seems to be coming from the diff and maybe since the subframe mounts are old, the noise is being transmitted more effectively to the cabin.

I still need to have a look-see at the ring and pinion gears one of these days to see how much wear is on them and check the preload on the bearings.

Has anyone priced a new ring gear and pinion gear (that is, if they're still available) from the dealer parts department?

Curt

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NoSnooz
Grand Rapids MI

84 190D 2.2 Auto 228,000

Usually differentials start whining when they wear out, due to an increase in the gap between the drive pinion and the gear. How about putting a custom made adjustment shim between the satellite carrier and the gear to move the gear closer to the drive pinion?

This should reduce/stop the whine and also minimize the "clunk" you feel when you are accelerating and suddenly release the accelerator. The same thing when you park the car and it rolls a bit before reaching the transmission park mechanism.

Any thoughts?

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1982 W123 300D NA Euro, 300K Miles, 4-speed manual, 3.46 rear diff, early W126 front brakes, Penta rims with 205/60R15 FH900's, custom fitted (by me) audio system, more to come into the money pit... Soon to be installed: Bilstein HD, R107 front discs and 4-piston calipers, HD Suspension springs, wagon front swaybar.

I suppose if the ring and pinion gears don't have too much wear, one could shim it up behind the pinion (I wonder if those crush sleeves are still available... I think I'll need one plus a couple side bearings and seals too).

I'm hoping to get the bathroom tile project done so I can start farting around with the car again.

On another note, I managed to get some time tonight to make a steering gearbox adjustment and it seemed to tighten things up.

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NoSnooz
Grand Rapids MI

84 190D 2.2 Auto 228,000

Not to hijack the thread...

The whine he refers to could be the bearings wearing out not the gears... It takes a lot to do damage to the gears, you really have to try destroy the diff gears along with the tranny.

to make sure its the differential i would get yourself a stethoscope(locally at autozone) and run the car on a lift. Use the stethoscope and make sure it is not the wheel bearings. Bad wheel bearings can be easily mistaken for a bad differential bearings when in fact it is the wheel bearings.
Good diagnosis will save you a lot of headaches...

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

But wheel bearings rumble, not whine, right? Don't wheel bearings make noise when taking a corner while driving? If so, it should be a bit easier to diagnose.

If bad bearings could make a whining sound, then it possibly could be the diff side bearings also.

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NoSnooz
Grand Rapids MI

84 190D 2.2 Auto 228,000

no....

bad wheel bearings make a whining noise and increase in pitch the faster you go.

CV joints make noise when you take turns not wheel bearings.

So yeah differential side bearings could be shot.

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)