BMW: BMW E30 325i Differential, ring and pinion gears, limited slip differential

Question
Hi There,

My Automatic BMW E30 1988 325i has a howling noise in the Diff and my machanic in Australia said it will cost $1000AU to get another second hand one. I reckon I can source one out somewhere else but I'm not sure what type of Diff to get cause there are so many types, Open diff, locking diff, slip diff? and different ratios.

What should I be looking for?

Regards
Kegan

Answer
Kegan,
 There were several differential ratio's available, depending on where you live (country) and what type of car.

 The 325i usually had a "limited slip" differential, at least I've never seen one that doesn't.  You're in Australia so I'm not sure what was offered there.  

 The noise could be bearings, but is most likely the ring and pinion gears grinding against each other.  The mechanic should be able to replace the worn parts and not charge you for a whole remanufactured differential.  It will still be pricey ($500-$600 US), but it beats $1000.

  The problem is that I dont know what is available to you there, and shipping something from the US would negate any savings you would have.

 Good luck,
 Josh