O1E (6 speed) Gearbox, causes of whine?

[Quattro Dan.]

I have a S2 ABY 6 speed gearbox in my S2 that has started to whine.

The whine noise gets louder the faster the road speed is and its the same in all 6 gears.
(Anyone that has driven a transit/sprinter van with a whining rear diff will know the sound.)

whine is definately from the gearbox, not prop or rear diff, confirmed using a stethascope on the 2 post ramp while doing 60 mph

When accelerating or slowing down the whine is evident. However, under balanced throttle I can almost get the noise to disappear.

Is the whine caused by the front diff crownwheel and pinion gauling, front diff bearings or maybe mainshaft bearings?

Any advice is much appreciated, thanks in advance, Dan.

Will a 01A (5 speed S2) front diff be a direct replacement for the 01E (6 speed)?

[Pirvu Eugen]

Are you sure the propshaft center bearing and joints are ok?
I would check these first before opening the diff's.

[TimE-J]

Also interested in the answers as mine has a whine that I'm sure is present in all gears but most noticeable in second and third, especially in second when changing down gears into second.

[Error404]

I have the same in mine, related to road speed not gears. I suspect either diff carrier bearings or input shaft bearing. I'll be changing gearbox later this year and will open the old one to have a look
Mines been wining for 6k HARD miles, not too much of a concern just yet but is getting slowly louder. As with most things with gearboxes the quicker its attended to the less expensive it is... but I'm not planning to repair mine.

[Quattro Dan.]

Are you sure the propshaft center bearing and joints are ok?
I would check these first before opening the diff's.

The noise is from inside the gearbox but I may run it up to speed (on the ramp) with drive shafts and propshaft removed just to be certain (when I get time).

Thanks, Dan.

[UrS4boy]

There was a recall on some of the first UrS4 01E 5 spd transmissions in North America. The whine was caused by improper pinion bearing set up. Whine increased with road speed.