Questions about an '89 Quattro 90

[alex@neth.com (Alex Neth)]

 Hello, I have a few questions for everyone,

    I just bought an '89 Quattro 90 that has been excellently maintained
by a dealer in Northern California.  There are a few issues I have with
it though
    Often when the engine is cold (if 80 degrees could be considered
cold), the engine makes a strange noise that sounds like metal clanking
against metal.  It occurs in synch with the revolutions of the engine
and increases if I rev it.  Sometimes it goes away and comes back.  If I
rev the engine high, it seems as though whatever is clanging skips off
of whatever is spinning and is quiet momentarily.
    The previous owner, a very nice family man dumping the Audi for a
larger Volvo, said that the car had made this sound since he bought it
in New Jersey 8 years ago.  Indeed, I confirmed on many of the service
records that he had asked them to look into the sound, but there was not
a firm conclusion and apparently they told him it wasn't a problem.
    I had AAA look at the car before I bought it and they noted only a
few small problems.
    I've been told the sound is not a problem, but it is relatively loud
and annoying.  I hate driving through a parking lot with my engine
clanking away.  The sound is very unnerving.
    Anyone have any idea what this could be and how to at least quiet
it?

Could someone also explain to me these problems AAA discovered and tell
me how important it is that I repair them soon?  This is what they
found:
    1) The rear differential needs to be resealed.
    2) I need to replace the front right outer axle bearing
    3) The upper strut plates are loose
    4) He also said the coolant and heater hoses 'appear original' -
though I've heard they last 100-125K miles and this car has only 73K.
    5) He said the timing belt should have been replaced by now, though
he didn't know if it had been.  The previous owner had done all the
normal services including 60K and 75K (early).  Would they have changed
the timing belt during this?  Can I tell easily?

Also, what's the best kind of oil to use in this car.  I've been told it
makes a difference.  How often should I change it?

Sorry for putting so many questions in one mail.  I'd appreciate any
replies.  Please mail me directly as well since I get the digest and
don't necessarily have time to read everything.

Thanks again.

--
Alex Neth
<alex@neth.com>