There is one that is almost exact as the sm420 except synchro low gear nice in traffic !
I'm not aware of any Saginaw 4-speed with a first gear ratio anywhere near the 7.05:1 of the SM-420. These two transmissions are not in the same league...
Don't rule out a broken speedometer cable. I just had one twist off 3" in from the trans end...
Mike B
