Gearbox woes

[David Boyd <john@dboyd.demon.co.uk>]

I posted a message to the List a few weeks ago re a replacement manual
gearbox (second-hand) I had bought for a '89 Audi 100 (non-quattro), which
appeared a direct match, even down to part nos., but it was not noticed
until trying to connect the driveshafts back to the flanges that the
replacement gearbox flanges were tapped for M8 bolts, not M10 as original.
The Supplier had been adamant it was the correct box, but subsequently
double checked and admitted it was the wrong one - he'd sent an AKM (?) type
instead of an AMK.

The box was replaced because it was extremely noisy.

Replacement no. 2 from Supplier fitted OK but the same noise is still there,
albeit much diminished. Supplier suggests that source of noise may not be
gearbox at all - wheel bearing main suspect. But why is the noise much
quieter since the replacement box ??

I'm going to get the wheel bearings listened to in turn whilst wheel off
ground and driving to see if this can be isolated, but has anyone else BTDT
?

I will attempt to describe said noise:

A low-pitched whine, which is constant in all gears *and* when freewheeling
in neutral. Starts at about 20mph and settles down to a constant whine at
about 50mph and stays like that irrespective of further speed increase.
Whine increases just very slightly when engine under load, e.g., up an
incline. Was extremely loud indeed with 'old' gearbox, but now just
irritating. Whether the gearbox/oil is hot or cold doesn't seem to affect
the noise level.

I suppose it is possible that replacement gearbox has the same fault but
less advanced than the original, but the Supplier (who is a gearbox
specialist and appears competent) assures me that the 'correct' replacement
he supplied has had new bearings throughout. He also says he has had a close
look at my original box and can see nothing obviously wrong with it. He is
located c. 170 miles away, so can't easily let him try to diagnose said
noise.

Why is nothing *ever* straightforward ??

BTW, I also have a 3sp auto Audi 100 ('91) and this 'expert's advice re
these is that *all* the wrecked ones he has encountered to date have
resulted from failure of the diff. to gearbox oil seal, and he therefore
strongly regular checking of the diff. oil level to give early warning of a
problem before it wrecks the box.

I am getting very p****d off with this, so any suggestions would be very
welcome indeed.

Regards

David

john@dboyd.demon.co.uk
Cumbria, UK.