Abstract: A hill holder cooperates with a countershaft in a vehicle transmission to permit rotational movement thereof in one direction while preventing rotational movement thereof in an opposite direction. The hill holder includes a cylindrical housing which is supported on a rear wall of a bell housing of the transmission in co-axial relationship with the countershaft. A clutch assembly is provided in the hill holder for selectively connecting the countershaft to the housing to prevent rotation thereof in one rotational direction. The clutch assembly includes a hub member which is secured to the countershaft for rotation therewith. The clutch assembly further includes a reaction member which is axially movable relative to the housing, but is restrained from rotating relative thereto. Mating ramp-shaped teeth are formed on adjacent end faces of the hub member and the reaction member.

Abstract: A hydraulic actuating system for disengaging a clutch, shifting gears in a transmission and reengaging the clutch for a vehicle. An electric pump delivers hydraulic fluid under pressure to an accumulator. High and low pressure switches control operation of the pump to maintain the hydraulic fluid pressure within a desired range, while limiting operating time of the pump and minimizing energy waste. The pressurized fluid from the accumulator is applied through valves to operate a clutch actuating mechanism and to shift transmission gears. A secondary accumulator is provided at the clutch actuating mechanism to provide smoother clutch reengagement with a low cost valve having a relative coarse modulation capacity.

Abstract: A vehicle mechanical transmission includes a conventional shift lever which enables the vehicle driver to manually select lower gear ratios, and an automatic shifting mechanism which provides automatic shifting between selected higher ratios once the driver has moved the shift lever to an "automatic" position. The transmission includes a plurality of shift rails which are individually and selectively moveable from a neutral position to two different gear positions. In accordance with the present invention, the shift lever is only coupled to mechanically shift a portion of the shift rails, typically those shift rails corresponding to the lower gear ratios. Once all the lower ratios have been selected, the driver can move the shift lever to an "automatic" position. When in this position, the shift lever actuates an electronic control, which in turn automatically controls the shifting of at least one shift rail in accordance with the status of various monitored vehicle operating parameters.

Abstract: A transmission synchronizer includes a strut and blocker ring engagement system wherein the strut is retained by the blocker rings in all of its axial positions against centrifugal and spring forces on the strut. The slots in each blocker ring are fully enclosed, and thus are disposed for total containment of the opposed ends of the struts. In a preferred embodiment the strut includes a pair of opposed axially spaced, radially extending bearing surfaces, each disposed for axially bearing against one side of a blocker ring, wherein each of the bearing surfaces is distinct from the slot engaging ends of the strut. Thus each bearing surface defines an inwardly stepped wall relative to one of the slot engaging ends of the strut.

Abstract: A free ring synchronizer is provided with improved resilient means for circumferentially biasing a pair of axially spaced friction rings in opposite directions. The resilient means is a coil spring mounted within a shiftable coupling collar interposed between the friction rings. The coil spring includes radially extending legs for engaging oppositely extending pins which are fixed to the friction rings and pass through openings in the shiftable coupling collar. Coacting blocking surfaces are provided on the pins and in the coupling collar openings and are releasably held in contact by the reaction of the legs against the pins.