Leaking Diff

I noticed a damp patch underneath the rear of the car and I assumed it was condensation from the exhaust

Although a closer inspection (smell) told me if was diff oil.  I had a good look around the diff and concluded it was coming from around the fill plug.  The level of the oil should be below the fill plug, but I have had the car at all sorts of angles lately so could have been that.  

I tried tightening the plug, but it was tight.  So I removed it for inspection.

The diff identification plate sits underneath the plug which I think is strange since it isn't a sealing washer...

On close inspecion of the plug, I could see an un-even mark - possibly caused by this identifiction plate.  I decided the plate would not be going back on, and I removed the step from the plug in the lathe.

I thought since I was in the diff, I would change the oil - it came with oil from the factory but I thought best to change it.  I spoke with Andy and got the newest spec of oil - (BTR Hydrotrack LSD:  recommended, Morris Lubricants Lodexol XFS 80w/140. Approximately 2 litres)

I drained the old oil out (the drain plug is also used as a diff cover bolt), re-fitted the drain bolt using threadlock and a seal, and filled the diff.  I put in 1.72 litres.  I put a Dowty washer (bonded sealing washer) on the plug and I left the ID tag off.  Problem solved.

Diff as it arrived

Diff as it arrived

Pre-Machining - You can see a raised section on the sealing face

Sealing face machined flat