Additionally the lockout on the shifter itself could be due to the ratios available in the box, if one ratio is pretty big like 2.0:1 and the rest are close like 1.2:1 it may have been used to lock out the deep ratio while on the road?

1946 Chevy Pictures
1946 Chevrolet 2-ton. In family since new. Splash oiled 235, 4 speed main, 3 speed aux, single speed 6.17 rear. Original GM supplied 12' stake bed, paint on sideboards is still from the factory.
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