Abstract: The automatic free wheeling hub assembly includes a housing or body secured to the vehicle's wheel hub. The vehicle's drive axle extends into and is mounted in the body and wheel hub. The free wheeling hub assembly includes a cylindrical axle hub located in the interior of the body and spline connected to the splined end of the drive axle. The axle hub is provided with an external toothed section or series of circumferentially spaced teeth. A tubular clutch ring is mounted in the body for axial movement and is provided with internal teeth for engagement with the disengagement from the series of teeth provided on the axle hub. Fluid actuating means are provided in the body including a movable member in the form of a diaphragm or piston connected to the clutch ring for axially moving same relative to said axle hub in response to the pressure or pressure differential from a fluid source such as vacuum to effect the engagement and disengagement of the matching teeth of the axle hub and clutch ring.