I was saying that to from low to 2wd high, say comming of a track onto tarmac, all you need to do is push the red knob, no need to use the yellow knob (I've only ever used that when driving on snow).
Surely to go from 4wd High to 2wd High, just press the clutch, pull red lever back, yellow knob jumps up, push red lover formard and off you go.
Undoubtedly - I suspect that Series motors never regained full-time FWD until the Stage I simply due to Leyland's financial woes. Your diff lock shouldn't go bang - just push the lever away from you and it's engaged, and vice-versa - as long as you don't change ratios you can do that at any speed.
Richard