huesey1974

Hi guys,
Ive been doing a lot of motorway miles in the last week and i have noticed a slight whine that increases with speed, I cant really hear anything until about 55mph and its drowned out at about 75mph.Im sure its coming from the rear end of the car and was hoping for some advice.I was thinking of changng out the diff oil as the car has loads of history but nothing saying the diff fluid has been changed.Any advice greatly appreciated.
Thanks

Glyn M Ruck

Suggest you replace the diff oil with the approved stuff.

These cars when fitted with the M112/722.6 combination like yours do hit a harmonic at approx 55 mph, 90Km/h where you hear some sympathetic whine with the diff. Once you drive through that speed it shuts up. The M272/722.9 combination does not do this. It happens on W203 & W211 as well with the M112/722.6 combo - The NVH engineering is not perfect.

The only time you should be worried is if there is a substantial difference in noise between accelerating & trailing throttle which would be a sign that the pinion bearings had lost preload.

huesey1974

Hi,
Update time, Last night i changed my diff oil which was very much black and really stinks.The whine is still there, Im sure it only starts at around 50mph and cant hear it at 80, Dropped the car out of gear at 65 and the whine stayed as it was.Anything else i could look at? Had a gearbox go b4 on my BMW so im hoping it aint that.
Thanks

Glyn M Ruck

It's likely diff or tyres. Run your hand over your tyres counter rotation a feel for feathered edges on the tread - this can whine.

Other sources of a whine could be a wheel bearing or centre propshaft bearing.

huesey1974

Hi Guys,
Just to update, I changed my rear tyres and all is silent again.

togaclk55

Glad to hear the good news. Yet another win for Glyn .

mikata

That explains alot. Great info Glyn!

Louie D

+1 for the Caped Crusader

Glyn M Ruck

Great to hear! This chassis is sensitive to tyre selection & any cupping or feathering can cause audible air pumping noise that sounds like a bad bearing.

Kevwood

Pretty sure this should be Glyn & Rod's avatar pic;

Rudeney

I can't speak for Glyn, but you definitely don't want me running around in a spandex unitard.

Glyn M Ruck

My portly frame would look outrageous in spandex.

dvpriem

I have a new 2013 E class 350 with 200 miles on it. There is a whine under slight acceleration between 70and 75 mph. There is no difference in the sound if I change to a higher RPM in 6th or 5th gear. It always occurs under slight acceleration in the same speed range. There is also be a similar sound between 50and 55 but not as loud. I will take the car in soon. What do you think the service people should do? I ask because the dealership is 125miles away and I don't want to go back and forth.