Marcus,
You did drive it for the better part of 2 or 3 hours with only one driveshaft coupling. The other wheel could have been breaking adhesion and spinning out of control for a lot of the time, even with the difflock on.
Perhaps this did the damage that is now manifestering
Plus the VC was an unknown quantity, with that replacement diff....
So don't be too hard on the old girl. Ok, quite new girl mileage wise!
Whilst people say they last x thousand miles on average, a few incidents of prolonged overheating can dramatically reduce their lives.
Dunno what Syncro-Nutz charge, but it's the cheapest, quickest and best way of guaranteeing an even better season this year. Probably around £400 for their refurbed ones, and you even get a calibration graph with it, cor
P.S. Perhaps we'll all be the wiser in future, maybe not proven, but there's a good chance driving gently home on tarmac is about all you should do when a front-outer breaks up, maybe with the prop off too.