Robbie
As above I not heard of a BTR diff failing except in competition cars.
Has it been run dry of oil by any chance?
The Quaife upgrade (from Richard's link) is a well respected upgrade as it gives a much more "progressive" take up of the drive to both wheels. If the diff does indeed need replacing then go for this every time.
The best person to talk about Morgan diffs across the whole range is Billy Bellinger at JB Sports Engineering
https://jb-engineering.co.ukHe deals with everything from Series 1s , through Sailsbury axles to BTRs. A true enthusiast (and a vey good racing driver) who I can recommend 100%
