Mr needy needs diff help

[spock505]

That's how it feels, asking so many Q's about this car but the list is shortening.

To cut a long story short, the vehicle (S124) had a variety of whines/whistles and general bearing noises when originally purchased.

These have now been reduced to a single high-ish pitched whine in 2nd/3rd gear speed range.

Popped the car up onto ramps Monday with two experienced mechanics (plus me), one of which specializes in classic 124 Mercedes amongst others.

The good news is it appears to be coming from the front diff nose bearing, but unsure as to why. As part of the noise elimination a replacement diff was fitted (getting rid of low down grumble), it is the same size and ratio but obviously off another car.

I played around with the height by turning the washer (marked with red arrow) upside down, this made no difference. Has anyone come across alignment issues/noises with replacement diffs?

There's no vibration at all either visually looking at the prop in gear under power or when driving.

Any thoughts greatly appreciated.