Thanks for all your help guys!!! This is certainly a big job for a fluid change. I will definitely consider doing this some time soon, but as my gear changes are silky smooth, I may get it done in a year or so. Other important maintenance issues to take care of. I think power steering pump will come first. May sort my diff out as that it simple enough.
Cheers again and Steve ill prop contact you when I need some work done on the tranny.