^^^ in 421 gear box there are 4 levers to operate from:
1) main gear four point lever
2) two point lever for reverse and forward
3) two point lever for low and high ratio
4) three point lever with 2x4, 4x4 and 4x4 with diff locks
when you slect the forward gear you have 4 forward option to select from either you want to drive 2x4 or 4x4 either in low or high. when you slect revese you have 4 reverse ratios to chose from main lever either you want to revers in 1st, 2nd, 3rd or 4th gear and low or high 2x4 or 4x4 or 4x4 diff lock. so if you are not able to go forward you have the ground control to reverse with a massive gear box power
5) optional PTO drive lever that i think only my mog has so far in pakistan.
6) optional 2 speed crawler gear attachement to gear box but you can either attach PTO or crawler at one time.