Apologies if this has been covered before but I couldn't find anything using search.

I've bought a 'used' Ford Sierra/Granada 7.5" diff of unknown history.

Before fitting it I wanted to check out it's condition.

The input and output flanges rotate freely without any undue noises or backlash.
I then removed the magnetic oil filler level plug and took a sample of oil. The oil is clear, amber colour and new looking but there was a small cluster of swarf accumulated on the magnetic plug. About a dozen tiny pieces of metal.

Is this normal or does it suggest the diff is worn or damaged.

Should I remove the back cover and inspect the gears? If I do remove the back cover, what am I looking for?

What sealer should be used when replacing the back cover and is there a recommended torque for the cover screws?

Thanks for any feedback,

Peter

gearboxes and diffs produce swark. Only a worry if it is big bits or teeth.
So just a drain and refill with fresh oil would be my approach.

You've done the usual checks and it seems fine, So as above I wouldn't be too concerned and just replace the oil with the correct spec

Their a popular & robust diff and used by many

To be fair if the drain plug hadn't been magnetic you probably wouldn't have seen much/any swarf anyway?

Any instant black gasket will be fine, so long as the breather is clear there should be no build up of pressure anyway. As for bolt tightness, not mental is just fine and if it's worn you'll know all about it when it's on the road. If you do open it up, there's not very much to see or assess, while the chances of a broken tooth or bearing failure is extremely remote. Personally, if it is not making any weird noises I'd just leave it alone and give it an oil change.

Thanks everyone for your advice.

[Edited on 28/3/24 by pfedwards]