That is a ratio change gearbox to make the speedometer read accurately when changing ratios in the 2 speed rear axle. When you move the selector to change from high to low, etc., the speedo reading will change before the axle does.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!