rotated to the position shown in fig3 fingers 87 and 89 enter the depressions and retain sun gear 20 out of engagement with planetary pinion 21 notwithstanding vibrations to which the equipment is subjected during high speed highway travel as can be seen most clearly in fig2 and 3 the excisions in cylindric skirt 103 of actuator 89 form spaces axially outward of camming surfaces 104 and 105 the excisions are of generally triangular shape and are bounded by circumferentially oriented surfaces s opposite camming surfaces 104 and 105 the maximum axial distance between surfaces s and the camming surfaces exceeds the distance of travel of sun gear between the engaged and disengaged positions accordingly if actuator 89 is rotated from the disengaged position of fig3 to the engaged position of fig2 and if the teeth of sun gear 20 are not aligned with spaces between the teeth of all planet pinion gears 21 subsequent engagement of gears 20 and 21 occurs when rotation of planet pinion gears occurs and without further operation attention for locking actuator sleeve 85 in the inward position at which sun gear 20 meshes with planetary pinion 21 there is a latch mechanism 107 mounted on housing 79 latch mechanism 107 includes an externally accessible finger grip or knob 108 to which a radially extending locking pin 109 is rigidly fastened spaced slightly above the inner extremity of locking pin 109 is a cross pin 110 against which one end of a compression spring 111 bears compression spring 111 circumscribes locking pin 109 and the outer end thereof bears against the surface of a threaded plug 112 which retains locking mechanism 107 within housing.