Humming final drive W124

[Richard.Wilson]

I'm getting concerned about a noise from my W124 230TE, the final drive makes a humming noise (best I can describe it).
I've only had the car a few months and it's always been there, just started to bother me recently. partly reading of the others with the prop gaiters slapping.
This is different I think, as it is more of a humming or low-pitch drumming noise. It starts at about 40MPH and goes on linear to the road speed to the better side of 80 before it gets drowned out by the other noise.
I recently changed the Diff oil (used EP80/90) and found the old oil smelled really odd, not like Hypoid, and thin as p*ss. Seemed to be more like engine oil, but with a weird smell. I checked the flexible couplings, gearbox mounts, and for play in the bearings at the gearbox output and diff, all seemed fine.
I'm thinking it is coming from the output of the gearbox, as it seems to be under the transmission tunnel, or even further foward.
I've never heard anything like it before. It's completely linear to road speed, louder accelerating than decelerating but still there.
Any suggestions

 

[dieselman]

Sounds like a rear wheel bearing.

Does it become louder or quieter as you go around bends, if so which way. Louder as yougo right indicates left bearing and vice versa.

 

[Andy]

Hi

Is the car fitted with ASD. If so this could account for the weird smell of the axle oil. The oil in the limited slip cars is different to the normal axled vehicles. Sounds like the vehicle has done a few miles if the axle oil has detieriated as much as you say. IE very thin. This is again where I disagree with MB and axle oil change. MB say there is no need. I think there is. At least every 36k.

As for your noise. I don't think its wheel bearing. Usually the noise is there from a speed a lot lower than 40mph. Usually close to starting speed. But it doesn't mean it couldn't be. But sounds like its more like maybe pinion bearing noise. If either of the above. Its too late damage already done. Just need to pin point which bearing is causing the noise.


RegardS

Andy @ www.mercedesservicing.com

 

[Mike Buley]

Rear diff Richard?
It wouldnt be the prop like mine. That sounded like the whole car was about to self destruct....BIG SCARY NOISE!!!
Mike.

 

[Richard.Wilson]

Further to my symptoms,
Seems the noise starts earlier than reported, maybe 20MPH when you really listen for it, but it's a really low frequency hum at that speed.
I'll check the wheel bearings, but it doesn't seem to alter when I go round corners, so I'm guessing it's not that.
"Pinion bearing noise" sounds like it needs more investigation, do you mean the output from the gearbox or where....not sure of the description?
I wasn't aware that a 230TE might have an LSD, figured that those would only be on 6-cyl ones.
I've got a print out of the Special Version Codes (built list) from a helpful spares guy at the local dealership, and it only mentions...(653)Sports Chassis with L.A. wheels, 8-hole. (420) Automatic transmission 4-gear.+ loads of other unrelated info.
No mension of ASD, although that's not to say it is not a mistake, because it also lists (664) L.A. wheel 7-hole star design 17 inch.....which contradicts the info above, and which are not fitted.

Cannot really describe this "humming" very well except that it's very low and builds up linearly with roadspeed. .......starting to bug me now!

Richard

 

[Richard.Wilson]

Guys,
Just went back over the service records, looks like the dealership changed the Diff oil every 36K miles, and used "EPX80W90" which I guess is merc-speak for EP80/90, like I used......so I guess there's no LSD.

Rechecked the bearing play at each end of the prop, and there doesn't seem to be any movement at all......not to say there's not a shot bearing, but I cannot feel any clunking.

??Richard

 

[jaques2k]

Maybe someone has use of this: I had a similar rattling noise from beneath the gearbox on my W126. I feared the worst, that the gearbox had some fault. But the sound was relative to the speed of the car, not to which gear I drove in. So I went under the car, and checked out the front coupling of the prop shaft (driveshaft?). There, one of the bolts was loose. I had to replace the bolt with a new one, and the rattle is gone, and now it runs like a dream!