Diff whining after seal replacement

[MPETT]

I had to pull over tonight due to a whirring sound only to find out that one of my newly replaced diff oil seals has failed and spurted oil all over my exhaust. Talked to my mechanic whom if dumbfounded having replaced circa 200 in his professional life. Having noticed on my return home on the flat bed truck 2 patches of oil on the driveway, it must have been leaking since I collected my car. I'm concerned that the diff will be knackered as I must have done 4 miles before I noticed the whine above the stereo. Fortunately I haven't been gunning it due to having just had a service 2 and letting the engine settle for 500miles or so. What do u guys think? Do I need a new diff/can the damage be detected if damage has been done?

A very sad e46 m3 owner

[MPETT]

I've been talking to a friend of mine who works at jaguar landrover and & a bit of a diff guru. He said to drain the oil checking for metal filings. If they are present, damage has been done but it may still work but there is a potential of noise being generated. If no filings them probably ok. It's best to fill up and drain twice to ensure all filings have gone then fill up again and go for a test drive.

My mechanic has ordered two new seals which should arrive today, so fingers crossed for no filings and two new seals that work!!

[MPETT]

Got a phone call from the garage and its bad news. Crown ring is buggered and needs replacing. He held his hand up and said it was his fault. he causght the new seal when installing the driveshaft. He even checked it back on the ramp after a shake down drive.

Even though he has made this mistake, I'm really impressed with him and the work he has done on my car to date. How many mechanics would hold their hand up high and admit responsibility when its going to cost them £1100 from their own pocket?