jumping out of gear [common on the old 3 speeds] is bad synchros or worn gears, not the shift box, who's only malfunction is jamming between gears - save yer money on that rebuild, for the trans
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics