First thing today was to go and pick up a diff. It's 3.92 open diff so a "diff"erent ratio to my existing 3.62
Lowers the top speed a little but it is still way above the national speed limit. Not planning to track it anytime soon so I'm not too bothered about that.
I want to just see if the clunking reduces. If it doesn't, it just means I have a spare diff :-)