At the end of the day, both the 3 and 4-speed transmissions have the same 1:1 hi gear, so nothing is really gained speed wise. The SM-420 just gives you a really low Granny gear for pulling/hauling a load up a hill.
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD
