Ok, this evening I removed the rear propshaft, check the UJ's properly, all nice and snug, took it down the bypass, whined like usual. Reinstalled the rear propshaft & removed the front propshaft, checked the UJ's all nice and snug again, took it for a spin down the bypass, all nice and quiet :-D. Reinstalled the front propshaft, took it for a spin down the bypass, whined again.... Front diff faulty??
Thanks
Dave
PS. Whilst removing propshafts I noticed there appears to be a bit of slop in the transfer box, perhaps 1/3 of a turn of the output shafts, normal??