You could remove the front prop and try driving in difflock. if there's still vibration fit the front and remove the rear. At least if nothing else it will rule out your props.
Stay away from the Loch lomond area as you will get moved on its also quite boring. You would be better off heading further north to glencoe or fort William .
It's very long but it dose quite well with the rear diff locker. it's just not good with big drops as it gets hung up. It's also interesting on the seesaw lol
I was in the red l200 at the top of the hill. did you join up on Sunday? There was a couple of bits I had to reverse on but there's always a easier way round the hard bit's. The danger sings are also handy lol
Almost just need to refit some pipe work and a quick check up at the auto sparkle to check it over and I should be good for next weekend . Although I'm free this weekend if you fancy a trip out