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Hi, i have S212 300 cdi 7G RWD with AMG Sport package and Airmatic suspension, year model 2011 with 380 thousand kilometers on it and rear end is making humming noise which starts at 40kph speed and stops about 100kph speed.
When i loose the pedal just a little that RPM drops to about 1500 then the noise is almost gone and all i can hear is some minor road noise.
The car just got new Conti tyres and new balanced rims, Febi driveshaft center bearing incl. support and driveshaft rubber joints, new Lemförder engine and transmission mounts, new MB original oil in the diff.
Theres no play in wheel bearings, no rattling or any "metallic" noises coming from rear end, just annoying humm when accelerating and coasting from speed... Rear subframe havent been replaced yeat by MB because car has been taken very good care through its life, but could it be that subframe mounts are a bit loose and tired and making that kind of weird humming noise for unbalancing?
Also it just got wheel alignments checked.
Car has been maintained very good through its life and kept pristine condition, in subframe theres only some visible surface rust with that mileage but nothing disastrous at all.
Thanks for the help in advance and sorry for my bad english.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Well, since you have the AMG Sport package with different size front and rear wheels, you can't easily swap them around. But it does sound like tires. Was there any noise before all the maintenance was done?
Yes, the noise was already there in the first place.
All the maintenance done including wheels and tires replaced. Car is now of course more silent than before with the new tires etc.
Ive come this far already so maybe just get new rear wheel bearings? It just doesnt sound like bad wheel bearing noise at all
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by flu91
Yes, the noise was already there in the first place.
All the maintenance done including wheels and tires replaced. Car is now of course more silent than before with the new tires etc.
Ive come this far already so maybe just get new rear wheel bearings? It just doesnt sound like bad wheel bearing noise at all
Normally, I don't think wheel bearing noise diminishes. However, I'm not a professional. BUT, you do have nearly 240,000 miles on the car, so wheel bearings may be it. I would have a professional make that determination before throwing parts at the car.
I forgot to mention that the car was inspected couple of weeks ago by professional, told him to check it good because of that noise and even he didnt find the source.
Its getting pretty frustrating and been thinking about sound deadening the whole trunk area 😆
There wasnt any metallic particles in old diff fluid and usually bad differential sound is more like grinding...
Still it can be possible if the gears are just little bit worn maybe?
There wasnt any metallic particles in old diff fluid and usually bad differential sound is more like grinding...
Still it can be possible if the gears are just little bit worn maybe?
Good job with all the troubleshooting and maintenance:
Humming likely from diff input bearing.
(not wheels)
Best course at that mileage is to turn up the stereo.
Absolutely no sense in rebuilding diff. now.
I would spend your maintenance dime on more important items than $2.5k diff job.
Suspensions
Engine
Tranny
...
+++ Do you want engine to last, for free?
Clean/replace dirty old oil bypass valve in filter cap.
Last edited by CaliBenzDriver; Oct 21, 2024 at 06:49 PM.
Thanks for the replies!
I'll look in to it and if its coming from the diff, the used ones here in Europe usually cost 200 - 500€.
In best case i can sort it out in this week with the help of pro mechanic and stetoscope and post here if we got any progress.
Hi, i have S212 300 cdi 7G RWD with AMG Sport package and Airmatic suspension, year model 2011 with 380 thousand kilometers on it and rear end is making humming noise which starts at 40kph speed and stops about 100kph speed.
When i loose the pedal just a little that RPM drops to about 1500 then the noise is almost gone and all i can hear is some minor road noise.
The car just got new Conti tyres and new balanced rims, Febi driveshaft center bearing incl. support and driveshaft rubber joints, new Lemförder engine and transmission mounts, new MB original oil in the diff.
Theres no play in wheel bearings, no rattling or any "metallic" noises coming from rear end, just annoying humm when accelerating and coasting from speed... Rear subframe havent been replaced yeat by MB because car has been taken very good care through its life, but could it be that subframe mounts are a bit loose and tired and making that kind of weird humming noise for unbalancing?
Also it just got wheel alignments checked.
Car has been maintained very good through its life and kept pristine condition, in subframe theres only some visible surface rust with that mileage but nothing disastrous at all.
Thanks for the help in advance and sorry for my bad english.
If it is the ring/pinion gear problem, it makes noise under load regardless of the speed (rpm).
You say it starts at 40 km/h and stops at 100 km/h. This all sounds like drive shaft issue (U-joints) or the shaft is not balanced correctly that excites the harmonic vibration in the speed range you mention. You say the part is new, but even the new one can sometimes have issues.
Never heard before that unbalanced driveshaft makes noise, and u-joints usually makes squeaky voice? Also the car doesnt vibrate or shake at all
This might be very far fetched idea but can sooty dpf make that kind of noise all the way through the exhaust? Never experienced bad dpf before so i dont have any idea how it might behave, and also it havent never been removed and cleaned from this car (no error messages though)
Never heard before that unbalanced driveshaft makes noise, and u-joints usually makes squeaky voice? Also the car doesnt vibrate or shake at all
This might be very far fetched idea but can sooty dpf make that kind of noise all the way through the exhaust? Never experienced bad dpf before so i dont have any idea how it might behave, and also it havent never been removed and cleaned from this car (no error messages though)
Bad drive shaft makes exactly humming noise. If balance is just slightly off it can make very small resonance vibration in the structures around it (not really shaking the car). like the channel walls it is mounted to.
Well now that you mention it, it kind of makes sense that unbalanced shaft can make some resonating noise under the back seats (these cars arent very well sound proofed anyway)
In next friday i take the car to the workshop and see if we finally find something out.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
I once had a U-joint lock up on a 1981 Volvo station wagon. The car felt like it was going to shake apart. There was an excellent foreign car shop I took it to, and they had to send out the driveshaft and have it rebalanced. After that, it ran beautifully.
We located the sound source today: its coming from the diff!
More specifically heard from the pinion shaft/bearing and from both side bearings.
Tried to do something in despair and added some X1-R to the diff fluids and drove it about 250 kilometers 😁 but no any difference in sound so far...
The smartest thing might be to start looking less used diff, but then again of course, they are always used but might be better idea than putting 2000-3000€ to new parts.
Is there any good additive that might be worth still to try? I mean the sound is not really that horrifying right now what i used to hear from some old 124's or Sprinters
Trying RVS T3 out of pure interest, that for it lasts 2-3 months longer when i have more time to get it properly done with new bearing set OR with lesser used diff with new bearings and seals.
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