Abstract: A pressure control system for a differential includes an input member and a pair of output members, a pump disposed to be driven in accordance with the difference between the speed of one of the output members and a reference, a chamber which is supplied by the pump, and at least one bleed passage from the chamber. A piston is responsive to hydraulic pressure in the chamber to operate a brake between the one output member and the reference. The bleed passage includes a plunger which is movable against a resilient bias in response to pressure in the chamber. Flow through the passage is blocked when the pressure on the plunger reaches a set pressure.

Abstract: A continuously variable transmission has a variable transmission unit which provides a variable speed ratio between an input member (2) and an output member (3). The output member drives an output transmission member (11) through a simple drive connection (19-23) in a first regime of the transmission, and by way of a power recirculation system (7-10) in a second regime. The transmission is arranged so that only a clutching operation is required to effect a synchronous changeover between regimes.

Abstract: A rolling-traction automotive transmission in which a rotary component is urged axially into contact with a second component by the force exerted by pressurized fluid contained in a space defined between the first and a third component, and in which that space is closed by an annular seal so arranged that the fluid within the space bears radially inwardly upon it, so putting the ring into hoop compression rather than hoop tension. The clearance between the first and third components may be "U"-shaped when viewed in axial section, comprising two limbs meeting at their radially-outward extremity; the first limb may constitute the space in which the force separating the first and third components is generated, and the ring seal may be located in the communicating second limb, in alternative constructions either very close to the outer extremity or more inboard, say at the half-radius.