Methods for modifying certain prior art automatic transmissions to strengthen the transmission and eliminate a tendency of the transmissions to fail as well as components for doing the same. Some aspects also include kits for modifying a transmission to increase the strength of the transmission. In some examples, the hydraulic system of a General Motor's model number 4L80E transmission is modified so that an overrun clutch is engaged in more modes of operation than the original equipment prior art 4L80E transmission in order to minimize a tendency for an overdrive roller clutch to fail.

A hydraulic control system for a transmission is provided. The hydraulic control system includes a source of pressurized hydraulic fluid that communicates with an electronic transmission range selection (ETRS) subsystem. In one example, the ETRS subsystem includes an ETRS control valve, a park servo that controls a park mechanism, a plurality of solenoids, and a park inhibit solenoid assembly. In another example, the ETRS subsystem includes an ETRS control valve, an ETRS enable valve, a park servo that controls a park mechanism, a plurality of solenoids, and a park inhibit solenoid assembly.

A hydraulic control system for a transmission includes a source of pressurized hydraulic fluid that communicates with an electronic transmission range selection (ETRS) subsystem or manual valve and a clutch actuation subsystem.

A hydraulic control system for a motor vehicle transmission includes a pressure regulation subsystem in fluid communication with a pump for providing pressurized hydraulic fluid. A manual valve assembly is in direct fluid communication with the pressure regulation subsystem, and is moveable by an operator of the motor vehicle between at least park, neutral, drive, and reverse positions. A default disable valve assembly is in direct fluid communication with the manual valve assembly, a default disable solenoid, and a default select valve assembly. The manual valve assembly is in direct fluid communication with the default disable valve assembly which is in direct fluid communication with the default disable solenoid and the default select valve assembly. The default disable solenoid enables the default disable valve assembly to enable three default modes of operation and the default select valve assembly selects between two of the three default modes of operation.

A drag torque reduction device for an automatic transmission includes a hydraulic controller with a diversion for excess cooling oil into an oil sump that is positioned upstream of a radiator relative to a flow of fluid to the radiator. The diversion includes a temperature-dependent, switchable aperture and a switching valve. The temperature-dependent, switchable aperture is configured to close above a temperature threshold. The switching valve is configured to close above a threshold pressure.

Saturation of a secondary system pressure circuit (18) of a hydraulic system (4) of a motor vehicle transmission is earlier, in that an excess amount of oil from a primary system pressure circuit (16) of the hydraulic system (4) is not directed to a suction charging (40), but rather into the secondary system pressure circuit (18). This can take place via a system pressure valve (9) for the primary system pressure circuit (16), which is configured for this function.

A hydraulic pressure supply system of an automatic transmission includes: a first hydraulic pump forming a first hydraulic pressure from a hydraulic fluid stored in an oil pan; a second hydraulic pump pressurizing a received hydraulic pressure to a higher pressure, where the received hydraulic pressure may be received from the first hydraulic pump and from the oil pan; a regulator valve which is disposed at an upstream side of a low pressure portion and regulates hydraulic pressures supplied from the first and second hydraulic pumps so as to supply the regulated pressure to the low pressure portion; and a plurality of hydraulic lines that supplies the hydraulic pressure of the first hydraulic pump to the regulator valve and a high pressure portion and supplies the hydraulic pressure of the second hydraulic pump to the high pressure portion and the regulator valve.

A drop-in lube boost valve assembly replaces an OE lube boost valve assembly in a vehicle transmission hydraulic circuit. The OE valve assembly has a valve body with inlet, balancing and outlet ports. The drop-in valve assembly includes a sleeve having inlet and outlet ports, and a bore extending between and fluidically connecting the ports. The drop-in valve ports are spaced from each other. The sleeve includes valve and spring chambers. A valve has a valve face, a sealing portion and a spring stem and is positioned in the sleeve with the sealing portion positioned in the sleeve bore. A spring is positioned on the spring stem. The valve reciprocates in the sleeve between an open state in which the sealing portion does not overlie the sleeve outlet port and a closed state in which the sealing portion overlies and closes off the outlet port.

A transmission assembly for a hydrostatically or electrically propelled vehicle, comprising an input shaft, an output shaft, a first pair of gears and a second pair of gears, a synchroniser, a hydraulically operated actuator of the synchroniser which comprises a rod, and a hydraulic circuit for moving the rod, wherein the rod comprises an enlarged portion that is slidingly and sealingly housed in a respective portion of the seat so as to define two intermediate chambers. The actuator further comprises a contact element that is slidingly and sealingly housed in a relevant seat that is adjacent to the portion of the sliding seat so as to define a first end chamber, the contact element being able to move independently of the rod and defining an end point of the rod. A second end chamber is defined in an end of the rod that is opposite the enlarged portion.

A continuous variable transmission (CVT) hydraulic pressure control device includes: a pressure regulation valve regulating an operation pressure of oil supplied to a friction element of a forward-rearward device; and a switch valve to respectively switch oil discharge paths through which the oil supplied to the friction element is discharged, respectively by a pilot pressure from the pressure regulation valve and an elastic force of a return spring. In particular, the oil discharge paths switched by the switch valve have oil flow resistances different from each other.