2007 ML 420 CDI front diff grinding noise
 

Hie i have an ML 420 CDI , my front diff lets out a loud grinding noise every time i take off flat foot (kickdown). But if i take off at partial load there is no sound , it's only at power take offs. The suspension has been checked and found to b sound. Could i be needing a new front diff or are there replacement parts i can order?

moved to W164 forum...

Get your vehicle checked with it on a lift, and the wheels spinning to see where the noise is coming from.
This will tell if it's the diff, tire noise, a wheel bearing, or even the transfer case.
Don't bother going to the dealer, they'll sell you one they've replaced the bearings on for $3500-$4000 + labor.
They don't have new ones anymore.

People wondered what they'd do with all those bad diffs, now we know.
Bearing kits can be purchased here. at benzexpert.com. Your total cost for repair (assuming it's the diff)
should be $650- $1000 tops depending on if your replace all the bearings and seals,
or just the carrier bearing, the most common point of failure, + labor, anywhere from
$500 to maybe $800. (I paid $500 in San Jose, CA 2 years ago)
Where are you located?
Sent you a PM.

Just drain your front diff fluid and you will see the metal flakes in the fluid. This means your diff bearings are shot. Order them online along with the seals and get a tranny shop to replace them. I paid about 700 labor and 300 for the parts. Also if the bearings are bad you can feel the vibration on top of the steering wheel horn pad when you drive.

Yes, it tends to emanate from the center of the vehicle.
In my case, you didn't hear it until you got over about 40 mpg,
would royally roar around 55-65, and due to the higher frequency, seemed to taper off if you hit 75.
The frequency of the whine increases with speed, as it is a one speed
diff.