The present application relates to a piston assembly for engaging two selectively engageable parts. The piston assembly has a housing defining a piston cylinder and a piston. The assembly also has a piston stroke limiter. The piston stroke limiter is configured to limit the length of a return stroke of the piston from an extended stroke position and a retracted stroke position. A crushable body acts between the piston and the piston stroke limiter and is arranged to reduce in axial length when a length of an extended stroke exceeds a length of a retraction stroke to maintain the length of the return stroke.