Help diagnose my noise!

[MBVitoria]

Hi hoping someone can help.

Vehicle is a 2011 W639 Merc Vito van. 2.2 diesel manual (RWD). Mileage is 220k but it's generally a good runner.

In the last week it's developed a whining noise when I'm driving and lift off the gas. The noise disappears when I depress the clutch.

It doesn't make any unusual noises when it's stationary and there don't appear to be any issues with the clutch.

I first noticed the noise just before it went to a garage for a new exhaust middle and back box and it's worse since then. I'm not suggesting they've caused it as it seems transmission related though.

Any thoughts? I'm guessing it probably involves some sort of gearbox bearing.

[GreenV8S]

I'd suspect a gearbox/diff issue too, although it's possible it's just a mechanical contact on a moving part due to engine flex.

Does the frequency / volume vary depending on which gear you're in and the amount of engine braking?

[stevieturbo]

Maybe they disturbed a mounting, or something is making contact where it shouldnt.

An oil change for the box might do no harm if it's never been done.

As these are rwd, maybe propshaft related ?

[CorradoTDI]

Sounds like clutch release bearing / slave cylinder / DMF / bent clutch fork etc.

I'd get someone who really knows these to try and pinpoint it!

[InitialDave]

Does it change pitch in different gears, relative to engine speed, relative to road speed etc?

That can often help narrow down what it is that's being vocal.

[MBVitoria]

Thanks for the suggestions. Had a quick look under and spotted that the exhaust heat shield fixings have rusted loose. The shield was catching on the prop shaft so that might help to explain it. Will have a proper fiddle in the light tomorrow and see if some penny washers can secure it.