The 240 4-speed works well, however it does seem like a long step between second and third. I spend a lot of time in third at speeds of 30-45mph. Maybe a 5-speed would offer more accommodating ratios in the mid-range. Overdrive may be nice, but 3000-3400 at highway speeds does not seem excessive, as the turbo is spooling nicely. My 300TD seems to be pulling strong at 110+mph, but is limited by rpm. How fast do you want to criuse?
Jacob