Job done !
Yesterday I added 2 oz of red line friction modifier to the valvoline 75W-140 in the diff and drove around for 1/2 hour , people were starting to stare as I was doing multiple 360s at the roundabout, the noise was much reduced , today I drove again and no noise at all so it would seem that BTR require more friction modifier than valvoline include in there LSD oil .
Thanks to all for your comments and advice.
Dave
Perfect day for a drive so off to waste some fossil fuel
