Torsional sleeve coupling

In combination:

• (1) a driveline coupling apparatus comprising a driving shaft, a driven shaft coaxially and matingly aligned therewith, both shafts containing splines at the mating ends thereof, a first sleeve splined to said driving shaft, a second sleeve splined to said driven shaft, said first and second sleeves comprising axially extending lost motion coupling means between said driving and driven shafts, said second sleeve comprising a third sleeve fixed to said second sleeve and extending circumferentially about said first sleeve, and (2) means for dampening torsional vibration between said driving and driven shafts comprising a counterbore in said first sleeve, a slotted aperture defining aligned sides in said first and third sleeves, wherein said aligned sides comprise interacting detents on said first and third sleeves, a C-spring positioned within said counterbore, said C-spring extending circumferentially about said driving shaft, said C-spring defining a pair of radial ears extending through said slotted aperture, said ears adapted for selective contact with said detents of said first and third sleeves, whereby in a first rotational mode of said driveline, said axially extending lost motion coupling means is positively engaged, and said ears of said C-spring are constantly urged together by said detents of said first and third sleeves, during which mode there is no lost motion between said driving and driven shafts, and whereby in a second rotational mode of said driveline, said coupling means is subject to lost motion, and said C-spring ears are disposed for absorbing torsional vibration between said driven and driving shafts.