Originally Posted by TomJ

Not necessarily the iron case that makes it better, but they were stouter because of it, kept main and lay shaft alignment under high torque and had stouter synchro's and gears. They were rated for higher torque than the later design aluminum one-piece case trannys (that had weak synchros and synchro springs.)

Also, I like the way they shift (feel more positive and firm than the alum, also a "shorter" shift), so I've swapped the alum out of the 300D conversion I did and installed one of the rebuilt iron cases and plan to do the same with the 240.