Keith
A few friends and I just had that conversation today. I would think that with the much wider powerband that the diesel has, the gearbox would not need as many speeds...leaving more room for larger gear profiles, bearing surfaces etc. I would bet that they were able to maintain the weight within reasonable limits while constructing a rather strong gearbox. With all that torque and horsepower on tap a little larger set of bearings and gears probably don't matter much. Of course like you, this doesen't mean I am not dying to get a close look at it!
Cheers
Phil