Whine/drone noise ML270

[loz_dormer]

Morning all, ML270 CDI 90k Miles,
I’ve got a whine/drone from when pulling away right up to around 40mph they it can’t be heard. It’s more noticeable when coasting along on a smooth Road and sounds very central.
I’ve had the car in the air and there’s nothing obvious, unfortunately you can’t seem to turn the ABS off to drive the car on a ramp to determine the location.
Ive changed both front and rear diff fluid with no change to the noise.
I suspect it’s the prop bearing or the gearbox but have no real way of proving this,
Any one had the same noise and had it rectified?
New prop bearing kit from merc is £180.

 

[oigle]

Have you eliminated tyres?
You can turn off the traction control to enable running one wheel in the air but the system doesn't like it a lot and takes a while to reconnect afterwards.
Doubt the noise would be hearable in an elevated position.

 

[loz_dormer]

I’ve swapped the tyres front to rear, it’s not them. It’s more of a bearing noise. If the cars driving in the air you can pin point the location, gearbox/diff/prop bearing. I don’t think it’s wheel bearing as it goes over 40mph and a wheel bearing would get louder with speed

 

[Mark A]

We had a failed prop bearing on the ML270 when we had it, was making a hell of a racket before changing it.

 

[loz_dormer]

I’m 90% sure it’s the prop bearing, I’ve just got no real hard evidence that it is the prop bearing I change it.
The list is getting longer on this ****** car