Abstract: An automatic transmission shift control system is provided for work vehicles, such as front-end loaders, which permits automatic shifting between first and second gears in response to vehicle speed but which inhibits downshift for a predetermined time interval after initiating reversal of the vehicle. A speed signal generator produces shift point signals at predetermined speed values and a speed logic circuit responds to the shift point signal for producing respective upshift and downshift signals. An inhibit circuit produces an inhibit signal in response to a reversing signal. The speed logic circuit is responsive to the inhibit signal for delaying the change from an upshift control signal to a downshift control signal for a time interval corresponding to the duration of the inhibit signal. The inhibit circuit is disabled when the speed decision logic circuit produces a downshift signal so that an upshift of the transmission may occur during reversal.

Abstract: A control circuit is disclosed for automatic lockup of a torque converter in the driveline of a work vehicle. The primary control for engaging the lockup clutch is a speed signal corresponding to the speed of the output shaft of the torque converter. A speed responsive signal generator produces a lockup signal at a first set-point when the torque demand is at a higher value and has a lower speed set-point for producing a lockup signal when the torque demand is at a lower value. A transmission responsive signal generator produces an enabling signal for torque converter lockup when the transmission is in forward drive above the first speed range. Shift of the transmission from one drive range to another produces a momentary disenabling signal to cause the lockup clutch to be disengaged and minimize driveline shock. Overspeed signal generator produces a disenabling signal to cause disengagement of the lockup clutch in an overspeed condition.

Abstract: An electronic reversing control system is disclosed for preventing excessive shock loading of the vehicle driveline when the operator calls for vehicle reversal with the vehicle in motion. A digital logic forward-reverse control channel links the operator's direction control lever and the reversing means in the transmission. When reversing is called for the control channel logic is inhibited by a speed responsive signal unless the vehicle speed is below a predetermined value. A speed retarding control channel controls the vehicle brakes and throttle when a reversing signal is produced provided the speed is above the predetermined value. Additionally, the system is provided with a logic power loss detector which resonds to power supply failure and automatically shifts the transmission into neutral.

Abstract: An electronic digital control system is disclosed for vehicle power transmissions, especially adapted for off-highway earth moving vehicles. Automatic forward speed range shifting is provided in response to the vehicle speed subject to certain overriding manual control. A transmission output speed signal is applied to a shift signal generating means which has a plurality of channels each corresponding to a different forward speed range. A level detecting means in each channel produces digital upshift and downshift signals and shift signal counting means, connected with all channels, produces a net count of upshift and downshift signal events and a command signal representing the speed range into which the transmission is to be shifted. A shift control circuit responds to the command signal to effect the required ratio change in the transmission.