pug there were indeed tandem axles on the cannonball rigs, but many were not what you are thinking. quite a few were "belt drive" off of the wheel separators from the front tandem to the rear. usually the rear tandems were a dead axle, or in some cases the front was a "pusher" axle. probably the 2 largest fleet purchasers of the cannonball was mc lean trucking and a company called riss. both are long gone, but both used the belt drive axles a great deal. the advantage was lighter weight and less power loss from the power divider and extra differential. some west coast companies like western-gillette, p.i.e. (pacific intermountian express),and brady used the full tandem. they were mostly a timken axle similar to the full tandem military trucks. as for overdrive, they were available, but not very popular near as i can tell. remember, the speed limits in those days was maybe 50 mph and on 2 lane roads. on the downhill stretch of a hill there was always "georgia overdrive" it is located in the middle of the shift pattern. you probably know it as neutral.
for many, many years the wheel separators or spacers for dual wheels were made to accomodate belts even though the belt drive system was basically discontinued around 55-56.
probably more than you wanted to know, but alittle history. oh yeah, about history. i know spanky knows the answer to this one. how many of you know how the term "cannonball" got to be associated with the cabover diesals? a hint might be the name mike malone.
