A chain tensioner for use on a chain drive system is disclosed which has a housing open at both ends. Into the housing, a cartridge is inserted, the cartridge having including a body with a cylinder within and a piston. A retention system is provided to substantially prevent the body of the cartridge from moving with respect to the housing. Such a retention system, in one embodiment, includes a lip at a first end of the body and a groove on a second end of the body. The lip serves as a stop to prevent the body of the cartridge from moving axially beyond the stop in one direction. A clip is interlocked into the groove on the second end of the body of the cartridge to prevent movement in the opposite direction.