Switch activated limp-home circuit for a power transmission

In a vehicle having a power source coupled to a transmission for moving the vehicle, a transmission controller coupled to the transmission to control the operation of the transmission, first and second clutches for engaging the transmission in first and second respective gear ratios, first and second clutch control elements for selectively controlling the engagement of the first and second respective clutches, a control system comprising:

• a manually operable gear shift lever having a neutral position and first and second non-neutral positions for generating a neutral signal and first and second non-neutral signals, respectively;
• a first relay circuit coupled to the gear shift lever and the first clutch control element and responsive to the first non-neutral signal to control the application of power to the first clutch control element;
• a second relay circuit coupled to the gear shift lever and the second clutch control element and responsive to the second non-neutral signal to control actuation of the second clutch control element;
• a manually operable limp-home switch coupled to the first and second clutch control elements to control actuation of the first and second elements, wherein the limp-home switch and the first relay circuit are coupled to actuate the first element when the limp-home switch is actuated and the gear shift lever is in the first position, to prevent actuation of the first and second elements when the limp-home switch is not actuated, and to prevent actuation of the first and second elements when the gear shift lever is in the neutral position.

In a vehicle having a power source coupled to a transmission for moving the vehicle, a transmission controller for controlling the operation of the transmission during normal operations, a plurality of clutches for engaging and disengaging the transmission, a plurality of clutch control elements for selectively signalling the plurality of clutches to engage and disengage, a limp-home circuit including a limp-home switch coupled to the clutch control element to permit actuation of the plurality of clutch control elements, a manually operable gear shift lever coupled to the transmission controller and having a neutral position and a non-neutral position for generating a neutral signal and a non-neutral signal, respectively, and a neutral latch circuit coupled to the gear shift lever and the plurality of clutch control elements for preventing the actuation of the plurality of clutch control elements until the gear shift lever is in the neutral position, a method of operating the vehicle in a limp-home mode including the steps of:

• disengaging the plurality of clutches from the transmission controller;
• disabling the neutral latch circuit;
• moving the gear shift lever to a non-neutral position;
• and
• actuating a limp-home circuit.