1987 300D Rear Noise - PeachParts Mercedes-Benz Forum

Marcb · #1 12-09-2005, 07:37 PM

Hello,

My 87 300D recently developed a "whine" in the rear area for some reason. I had new tires installed and replaced the front center link and the shop thought it might be the right wheel bearing. Had that one replaced and it still "whines" for some reason. The noise starts at about 35 and continues until 50 (or so) mph. If I coast in neutral, the noise is fairly pronounced and I'm wondering if it could be the left wheel bearing? I can't hear the noise when the car is at 70mph or much under load. I can't believe it would be the rear end but thought I'd see what you guys thought. The tire shop today looked very puzzled when I brought the car back in for them to have a listen. After searching several posts here, I tend to think bearings but wanted some different opinions.

Thanks!

#2 12-09-2005, 08:12 PM

Quote:

Originally Posted by Marcb

Hello,

My 87 300D recently developed a "whine" in the rear area for some reason. I had new tires installed and replaced the front center link and the shop thought it might be the right wheel bearing. Had that one replaced and it still "whines" for some reason. The noise starts at about 35 and continues until 50 (or so) mph. If I coast in neutral, the noise is fairly pronounced and I'm wondering if it could be the left wheel bearing? I can't hear the noise when the car is at 70mph or much under load. I can't believe it would be the rear end but thought I'd see what you guys thought. The tire shop today looked very puzzled when I brought the car back in for them to have a listen. After searching several posts here, I tend to think bearings but wanted some different opinions.

Thanks!

If you find out let me know!

Mine has been whining for about 35K and has not gotten better or worse. I posted the same question here and in tech a couple of times and although I got response, no body seems to know for sure why!

t walgamuth · #3 12-09-2005, 08:54 PM

doesnt sound like bearing noise to me.

maybe it is diff gear whine. benz diffs are supposed to be notorious whiners in the rear end. personally i never have noticed any though. and i have had quiet a few with more than 250k on them.

tom w

Brian Carlton · #4 12-09-2005, 09:10 PM

I'm inclined to believe it's the differential, as well.

The SD had a whine when it was just off road load. On decels or on accels, the whine disappeared. I was pretty convinced it was the diff.

So, during the renovation of the SD, I put a 2.88 in place of the 3.07 and the noise is gone.

Marcb · #5 12-09-2005, 09:20 PM

Do you guys still think it's diff whine if the shop couldn't hear any noise when it was on the hoist being run at about 40mph? It only made noise when the car was on the ground and on the highway. It does whine on deceleration right until it stops. You can coast, with the car turned off, and hear the slight "hum" sound until it stops.. it sounds like a rotational sound. I thought diff whine would also "howl" on the highway at 60-80 as well.. mine doesn't make any noise (that I can hear) at those speeds. The RR wheel bearing sure didn't make any difference. How bad of a job is a diff R&R?? Is it best to go used IF I have to go this route? I can't believe it failed all of a sudden.. but, I guess it could happen. Any more thoughts with the above details guys?

Thanks so much!

Marcb · #6 12-09-2005, 09:21 PM

One more thought... if it is diff whine, any suggestions on what oil I could try and put in there to quiet it down? I'm not sure when it was last serviced...

Thanks.

t walgamuth · #7 12-09-2005, 09:57 PM

it must be pretty loud if you are willing to change it out to get rid of the whine.

sorry to hear it.

tom w

Marcb · #8 12-10-2005, 12:17 AM

Thanks Tom.

It's not too bad yet... I just like having the 300D as "perfect" as possible... I will probably live with it for a while. I'm wondering if I should bite the bullet and have the other wheel bearing (LR) replaced for $150 and see if that helps...

Marcb · #9 01-15-2006, 07:36 PM

Well, the 300D is still making the same noise and I haven't replaced the left wheel bearing yet. Do you guys think I should try changing the diff oil? If so, what is the best recommendation here? I'm a little frustrated that the car is making this slight noise. It just doesn't sound right to me...

Marcb · #10 02-07-2006, 01:48 AM

Anyone??

ytr1903 · #11 02-07-2006, 06:14 AM

Get a used differential and install it. I think that Brian was right. I have installed two difs and am in the process of installing another. One dif change was due to noise as you are describing, another to put a 2.47 in a 300SD and this one to eliminate excess backlash. The job is not difficult. It does not need any expensive special tools, but does require some physical strength to remove and replace the actual pumpkin. The process is outlined very clearly in the Factory Service Manual.

Good luck,
Tom

dunl · #12 02-07-2006, 10:25 AM

I'd be curious to know about different gearing selections for a 300SD....why the change in ratios?

ytr1903 · #13 02-07-2006, 11:22 AM

I changed over to a lower gear ratio in order to quiet the car down on the highway. With the 3.07 factory ratio, the car was "busy" at highway speeds. The 2.47 lowered the rpm's by about 700 at cruising speed. Made me very happy. That said--your 1980 SD is a 116 chassis and probably(?) uses a different rear end than the 126 SD. I got mine from a 420SEL.

Tom

mbzkid · #14 02-07-2006, 07:45 PM

Check and top off the fluid level.

Ron in SC · #15 02-07-2006, 08:21 PM

I had rear differential noise, I called it a slight whine, on a 1983 240D. I bought car with 19K miles on it when it was one year old. It made the noise at 55mph to 60mph, the legal speed limit at the time and hence the speed it would be driven on the interstate.

The rear differential was replaced under warranty and I drove that car for years and sold it with 279K miles on it.

If the speed that your differential makes the noise is a speed that you regularly drive, then you need to get your diff. replaced, the noise will not go away.

Why some differentials are noisy
The rear differential noise is most probably from the ring and pinion gear. On one of my other vehicles where I disassembled the rear diff to replace friction discs for the LSD I would mention that the workshop manual indicated that the setting of the drive pinion and the ring gear is a determining factor for service life and smooth running of the rear axle drive. It goes on to say that drive pinions and ring gears are checked for good tooth contact pattern and low noise in both directions of rotation on special test equipment and are therefore matched during production. When I reinstalled the diff. I put it back with the ring gear contacting the drive pinon gear in the same position as when I removed it.

I'm sure mercedes does the same thing, but that some get by that should have been set differently or had new ring and pinions.