Mechanic says Carrier bearings UPDATE FIXED
 

I've mentioned in previous posts about a noise in the rear end of my 85 300SD. I took it to a mechanic I know and trust and he thinks the problem is the carrier bearings(sp?) in the differential. He said I should have that fixed/rebuilt or I would have to get another differential if I continue to drive the car. I also think it may be one of those deals that it stays loud but never fails completely. I need opinions on what I should do. This will be an expensive repair to say the least. The car still runs well and still looks good. Not to many other problems with it. But more failures are sure to come to a car of this age. This car has been in my family since 1991. Thank you for any input.

You could try changing the differential oil to a good synthetic (Like mobil 1 75w90 gear oil) and see if it quiets down. That worked for my dad's SD, an that was 40,000 miles ago.

You could always have a good used one put in too, way way cheaper than a new one.

With only 200,000 on it, that car has a LONG ways to go yet! Heck I BOUGHT mine with 207k 5.5 years ago....now its almost at 278,000!

Thank you. I think I am going to try that. I changed the fluid about 6 months ago but used regular gear oil. It was loud then but I am probably going to try synthetic.
I'm wondering about the differential. I believe I have read that the 85 300SD's had a different gear ratio than the 81-84 models? Is that true?

Has anyone here ever paid to have the carrier bearings replaced? Just curious of how much one should pay for this repair. I think I will be taking it to another mechanic that was recomended to me for a second opinion. More specifically for older Mercedes.

A carrier bearing is on the driveshaft not in the differential. It is the bearing/mount that hold up the U-joints of a mulitple piece driveshaft. Is the mechanic talking about the center support bearing on the driveshaft. It has a carrier bearing. That is much easier than rebuilding the diffential. It's not very common for the diffentials on these MB to go bad, unless it was running low on fluid.

Wups, you are right.

Carrier bearing is at the center of the driveshaft. I've changed mine, its a labor intensive process but not really that complicated. I'd do flex discs and center support carrier all at the same time.


Yes, the 1985 300D and 300SD have a 2.88:1 differential, while all the others have a 3.07:1 ratio.

Hmmmm, I'll have to find out more when I picked up. He said it was in the differential but I'll double check. I don't believe the diff has ever been run low. The car has always been regularly maintained. I changed the fluid not to long ago. But was to cheap to put synthetic in. Thank you for your expanation.:cool:

If the noise is at the back of the car then its the differential, if its under where you sit then its the carrier bearing.

I would change the gear lube and replace it with API type GL-5. This is the highest quality gear oil you can get and my Mercedes Dealership uses it too.

Consider this an opportunity to upgrade to a 2.47 rear end from an 85 500 SEL or equivilent. its about a 2MPG improvment.

From the way I understand it, the ring gear is attached to the carrier, and there are two carrier bearings on each side in the differential.

Now MB might call it something else.

I see the driveline bearing refered to as the center support bearing as well as the carrier bearing.

Charlie

I had carrier bearing changed twice in 350,000 miles on our 240D.
Symptom was kind of a howling/moaning coming and going. Shop didn't charge too much as I recall. Seemed to come and go with temp; ie as it got warmer was more likely to start a kind of resonance within the bearing. It definitely felt like it was under the front seat. The second time it happened I figured out pretty quickly what it was. Independant shop job easily.

+1. The differential does have carrier bearings. I've taken a benz diff apart and the carrier bearings have shims against them to provided the right amount of prel-load. Proper pre-load is essential so that the ring gear doesnt move too far to the left or rigth against the pinion. If the pre load is non existent, the back lash opens up and the diff sounds like its whining. If pre load is too tight, then things get too hot and you get pre mature wear. I'd look for a good used unit.

I've replaced carrier bearings on a SAAB. While it is in the transmission case (FWD), it is the same setup.

On that one, you measure the bearing preload with a piece of cord and a spring scale (like you would use for weighing fish). Then you take it back apart, install the pinion (measuring the projection), and reinstall the carrier with the total shim thickness that you used for the preload, but distributing the shims to the two sides to get the gear lash within specs.

It's a somewhat involved process.

My 81 240d makes a growly kind of sound when I accelerate and then back off the throttle and then get back on it. It sounds like at the rear of the car. I have drained and checked the diff for metal signs and found nothing so i refilled it and have been driving. Do the axle spacers wear out over the years as my axles look original. at 122k. Would side play make a growly noise? The axles do move in and out a bit in the diff and hub. which I guess is normal.
I looked under the car at the driveshaft and accompanying components and pushed, pulled and tugged on them with no real movement other than the DS moves forward and back a little but have not taken anything apart .
Any guesses here?