An improved scroll compressor having an axially movable non-orbiting scroll eliminates the need for a separator plate. With the elimination of the separator plate, a back pressure chamber is provided to resist the discharge pressure which will be directed against a rear face of the non-orbiting scroll. In other embodiments, a seal on the rear of the non-orbiting scroll contacts the inner periphery of the end cap. Various ways of increasing the discharge pressure volume, or eliminating undesirable noise are also disclosed. Further, several ways of connecting the end cap to the center shell are also disclosed.