Changing all the fluids in mine has made a huge difference, the guy who sold it me said it had recently been 'fully serviced'..however the front diff was mainly filled with water, the rear had some strange coloured liquid come out and the transfer box, well that didn't seem to have anything in!
As already said, ep90 for the diffs/transfer box and I used MTF 94 from the dealer for the gearbox (not too bad a price considering the dealership was more like a 5 star hotel lobby). Most if not all of my strange crunches/grinds/rattles/weird noises have gone, so well worth doing.
Don't forgot you'll also need a 32mm spanner and a torx t55 socket.