Crazy Drone in my Wagon! Please Help!
 

1995 E320 Wagon, 137K

My wagon has a very distinct noise present when driving. Its coming from the rear of the vehicle which leads me to believe it’s the differential…mainly because there aren’t any other components that I now of back there big enough to created a noise that loud (wheel bearings?)

The sound is loud and obvious. I sounds like bad tires, or you know then some jacked up jeep on mudders drives by. Just like that, kind of a low/deep whine or drone. So I replaced my dead 215/60/15 Goodyear Response Edges with brand new 205/60/15 Toyo Versados (whose selling point is quiet ride “technology”). I thought for sure that was the problem. I was wrong. Sound is still present. So it’s not the tires.

The sound also has strange characteristics. It’s not present until 25mph. then is “clicks On” and remains until I come to a stop then it starts up again. Its presence is also related to speed. As I slow down, it slows down. The most puzzling aspect of it all is the following. When driving at speed, say 45 mph and I take a long curve, like an off ramp, the sound will “turn off.” That is to say, when looking at the steering wheel, if a turn requires me to turn the wheel from 12 o’clock to 11 o’clock the sound disappears. The instant I return to center *BAM* the noise is back. Its borderline comical. I’d laugh if I wasn’t about to go insane from the drone.

I have not changed the diff fluid. I suppose any retailer should have mobile 1 syn gear fluid. And the dealership the diff gasket (didn’t see it on Fastlane). What’s the procedure for changing the fluid?

The car has ASR as well as the “snow chain mode,” not if sure those are related to this issue.

Do you have any idea on what it could be or what actions I should take?

have you ruled out a wheel bearing?
Gerard

Not a wind noise from the luggage rack bars?

I haven't officially ruled out bearings, but I I kinda assumed they were too "small" to make such a prominent sound. I could be wrong. They shouldn't be that hard to change no?

I would be very surprised if the luggage rack was the cause of this sound. but I'll pull them off - gotta try all the hypothesis right?

I vote for the bearings as well. if you can lift the vehicle, see if the wheels spin freely. On the 'way out there' hypotheses, could the emergency brake be sticking?

Been there on our wagon. 99% it's the cross bars on the roof rack. Depending on their position, they mess up the wind flow and make all kinds of racket. They come off. You could also adjust them to get rid of the sound.

The key is the attenuation of the sound when you jerk the wheel from side to side.

Cross bars would not be affected by this action. This is a classic wheel bearing failure symptom.

Jim

Sounds bearing-ish to me as well, however, once bearings start to groan they don't typically last terribly long..

I knew of one fellow who's wagon made a groan as described above, and had been doing so for over 10 years which led me to think it was the R&P alignment that had gone off some as opposed to bearing failure.

Jonathan

A 4-wheel alignment fixed it on my S420.

You might also want to look at flex discs and that center bearing on the driveshaft if your car has those items.

hehe, cross bars are not the cause and e-brake are good. but yeah I'm gonna head straight for the left rear bearing. the noise stops when I quickly steer left.

according to fastlane there is only one rear bearing and it looks like this.

http://img.eautopartscatalog.com/live/K802055001SKF.JPG


is there any "trick" or special tool on replacing this puppy? I'm assuming he's behind the hub. pretty much just start pulling everything off and I can't miss him?

My W126 did this a few years ago...
 

I had a 300SDL that did the same kind of thing you describe..

Driving straight on the highway there was a noise, but it went away when you went around corners in one direction. Straight away and the other direction produced a howl.

Here's what I tried (in order)

-Looked at axles and differential and boots.. all looked good
-Had MB tech look at it, he said "wait till whatever it is breaks, then we'll replace" as he couldn't find anything wrong
-Drove 3 more months and the sound began to get on my nerves.. took it back to him.
-He replaced left wheel bearing and said the old one looked "almost brand new" but that was his best guess. Problem still there

2 months later I decided to change the differential oil, and it TOTALLY fixed the problem! Waited 2 weeks and flushed the diff again and filled up with new oil, just to be safe. Drove 35,000 miles (approx) and the sound never came back.

Before looking at wheel bearings/etc, are you sure your differential oil has been changed?

My experience with my 129 was similar. I thought for sure the differential was going to grenade.

Turns out my right rear caliper piston was sticking. The pads were almost to the sensors at that point on that side. The other side's were in great shape.

I changed the differential lube in my 210 wagon this past weekend. Used Mobil 1 75w-90, the standard gear lube stocked in my garage. It may just be placebo affect, but I swear the car is quieter. And I thought that before I read this thread. I've always been a bit annoyed with how noisy the 210 wagon was at highway speeds. I assumed it was mostly tire roar, and indeed a switch from old Continentals to new Michelins helped. The diff lube change seemed to help just as much. It makes no sense, but I'll take it.

- JimY

changing the dif oil is also a good call. prolly should do if for no other reason than I've never done it and who knows if the prev owner did. whats the procedure, place bucket underneath and start pulling bolts? is there a gasket that will need to be replaced (fastlane shows no gasket available)? how do I fill, there isn't much room and I'm guessing there isn't an engine-oil-like-cap to simply pour it in.

you guys say that mobile syn gear oil is the oil of choice? no need for Benz stuff on these 95's?

Diff oil really should be swapped every 50-06K to keep things looking nice inside.

Just the two drain plugs is all...drain is rear pass side, fill is on drivers upper/middle of the side of the case.

I like Redline/Lubro Moly/M1 syn. diff oil...works great in all my cars and they get a Work out!

Jonathan