A rotary fluid pressure device defining a fluid inlet (17), an output shaft (37), and a housing (41,43) defining a brake chamber (61), a piston member (63,65) being disposed therein and biased toward an engaged position by a spring (69). Braking means (57,59) is associated with the piston and the output shaft, such that movement of the piston to the engaged position results in braking of said output shaft. The housing defines a fluid pressure port (73) in communication with the fluid inlet, and the piston defines a large pressure release chamber (71) in fluid communication with said fluid pressure port. The piston defines a small pressure release chamber (89) also in fluid communication with the fluid pressure port. A valve means (75,81) is operable, when fluid pressure in the large release chamber reaches a predetermined pressure, to communicate the large to a source of low pressure fluid.