Three (+) uses/benefits of the 1st gear in an truck with an SM420:
1. Win the slowest-truck race at an old-truck show (I did).
2. Burn rubber in first gear for 20-40 feet (to display smoking rubber, and/or, tire marks - impressive, to some people).
3. Easily start from stop when carrying/towing a heavy load (towing, for example).
4. Drag a VW bug up/out of a deep ravine (I did), without burning the clutch.
5. Never worry about getting stuck in gear when downshifting (as often happens with a worn/mis-adjusted 3-speed linkage).
6. Impress your friends by driving up the side of a barn (this is just a bad joke).
It does not give you lower RPMs at high speeds, compared to standard 3-speeds both are 1:1 in high gear.
