Yes, you can change the transfer box without removing the gearbox. I take the pto cover off the back of the transfer box(round cover to the left of the handbrake drum) and lift out the input gear(just slides out) to help lining up the replacement transfer box with the output shaft of the gearbox, makes it easier to fit as you can look through from the back helping you line up the gearbox shaft to enter the transfer box without damaging the oil seal. Slide the input gear back in, give it a turn to line up the gears and it will slide home, refit the cover.
cheers,
Stevie.
