Turns out my transfer box was a samurai/413, just over 2.5 turns i think it was. Now it's a 410 with the handbrake on board. Still on my 29" tyres it is lower gearing and is nice. Motorway driving isn't gunna be fun though!
Plus no whine no more!!!
So if 31s are the best size for an sj then I best go buy them.