Abstract: A method for controlling a powertrain includes operating a transmission in a neutral operating range state, monitoring commands affecting an input speed, monitoring a tracked clutch slip speed, determining constraints on an input acceleration based upon the commands, determining a clutch slip acceleration profile based upon the constraints on the input acceleration, determining an input acceleration profile based upon the clutch slip acceleration profile, and controlling the powertrain based upon the clutch slip acceleration profile and the input acceleration profile.

Abstract: A vehicle idle stop system is disclosed. The idle stop system comprises an engine, an automatic transmission, a first oil pump driven by said engine and generating hydraulic pressure which is supplied to a friction element of said automatic transmission, a second oil pump capable of operating and generating hydraulic pressure which is supplied to a friction element of said automatic transmission during an engine stop, and a controller. The controller is configured to control the engine to stop when a predetermined engine stop condition is satisfied, and to control the second oil pump to supply hydraulic pressure to a predetermined friction element coupled to a forward starting gear of the automatic transmission, the hydraulic pressure supplied to couple the predetermined friction element when the engine is automatically stopped and when a gear range of the automatic transmission is in a neutral range.

Abstract: Methods and systems are provided for controlling a vehicle engine coupled to a stepped-gear-ratio transmission. One example method comprises, in response to a first vehicle moving condition, shutting down the engine and at least partially disengaging the transmission while the vehicle is moving; and during a subsequent restart, while the vehicle is moving, starting the engine using starter motor assistance and adjusting a degree of engagement of a transmission clutch to adjust a torque transmitted to a wheel of the vehicle.

Abstract: Provided is a control apparatus for an internal combustion engine, which quietly restarts the engine with a reduced torque shock when a re-acceleration request is made by a driver.

Abstract: A control apparatus for a vehicular drive system including an electric differential portion and a mechanical power transmitting portion which are disposed in series in a power transmitting path between an engine and a drive wheel of a vehicle, the control apparatus being configured to limit an output of the engine according to a difference between an actual rotating speed of an input rotary member of the mechanical power transmitting portion, and a theoretical rotating speed calculated from an actual vehicle speed and a presently established speed ratio of the mechanical power transmitting portion, whereby reduction of torque capacity of an input clutch provided in the mechanical power transmitting portion does not cause an excessive rise of the rotating speed of a rotary member which is located on one side of the input clutch nearer to the engine, and an excessive rise of the rotating speed of an electric motor connected to the input rotary member.

Abstract: A method controls an automated dual clutch transmission of a motor vehicle. An actuating device, preferably arranged in the region of a steering wheel, for selecting the gear step of the shift transmission, which actuating device has a first and a second actuating element which, when actuated individually, cause an upshift or downshift of the shift transmission and, when actuated simultaneously, transfer the shift transmission into an idling state. When both actuating elements are actuated simultaneously, the force-transmitting clutch remains closed and consequently the selected gear remains engaged, and at the same time a clutch torque and/or an engine torque and, consequently, a drive torque acting on a driven wheel is reduced to approximately 0 Nm. It is thereby possible to tie up the force transmission again especially quickly after the termination of the idling state.

Abstract: An apparatus and method for controlling line pressure of an automatic transmission. A driving information detection unit obtains information. A shift control unit determines if a power-on downshift is requested based on the information of the driving information detection unit, and controls the line pressure based on if the power-on downshift is requested. An actuator forms the line pressure according to a control signal of the shift control unit. A pressure supply control unit controls supply of the line pressure to on-coming and off-going frictional elements of the transmission. The method outputs a first value of a line pressure control duty if the power-on downshift is requested; subsequently outputs a second, lower value of the line pressure control duty if a first shifting is started during outputting of the first value; and subsequently outputs the first value if a turbine speed is greater than or equal to a predetermined speed.

Abstract: A shift control device is provided for reducing a shock generated at a clutch engagement moment in a gearshift operation in a straddle type vehicle having a shift control device that makes the clutch operation and the gearshift operation using the power of an actuator. The actuator is controlled based upon a rotational position and a speed of a shift shaft. When the rotational position of the shift shaft is located between a first position and a second position, the shift shaft is rotated at a speed slower than a rotational speed at which the shift shaft is rotated before reaching the first position to engage a gearshift clutch at a low speed. The first position and the second position are set in such a manner that the gearshift clutch is in a halfway engaged state when the shift shaft is located at a rotational position between the first position and the second position.

Abstract: A vehicle drive system for adjusting vehicle fuel economy is described. In one example, the vehicle drive system includes an operator interface for adjusting vehicle operation so as to increase or decrease fuel consumption according to a driver preference.

Abstract: A shift control method of an automatic transmission controls a skip shift from a first shift-speed achieved by engagements of first and second frictional elements to a second shift-speed achieved by engagements of third and fourth frictional elements, wherein the engagements of the third and fourth frictional elements is controlled after completion of releases of the first and second frictional elements.

Abstract: A vehicle driveline control system includes monitoring when the transmission is in gear and the clutch is left open. If that condition exists for a selected amount of time, the controller provides an indication to the driver regarding the open clutch status. In one example, the controller alters the RPM rate of the engine to provide audible feedback to the driver. For example, the controller raises the engine RPM rate from an idle rate to a higher rate to simulate what the driver hears upon vehicle launch. A variety of indicators and control strategies may be used with a system designed according to this invention.

Abstract: A method of controlling an automated friction clutch arranged in a drivetrain of a motor vehicle in the force flow, between a motor and transmission, and the automated friction clutch is designed to be passively engaged by spring pressure and can be disengaged and engaged by a controllable clutch actuator. The automated friction clutch is provided with a path sensor for detecting the clutch actuator travel such that during the operation of the motor a current key point of a torque characteristic, provided for controlling the friction clutch, is determined and used for adapting the torque characteristic. With the friction clutch engaged and without the clutch actuator exerting any force, several values of the actuator travel are determined at intervals from which a current engagement point, close to the actual engagement point of the torque characteristic, is determined and with which the torque characteristic is adapted.

Abstract: In a method for parameter-related driver input gauging in motor vehicles, with the position of a moveable control element being determined, a theoretical maximum value of at least a parameter relevant for the drive system is defined and an actually recallable value of this parameter is determined. A change from a static to a dynamic driver input gauging is carried out below the actually recallable value of the parameter relevant for the drive system. A static gauging is carried out in a lower value range of this parameter such that the maximum displacement of the movable control element is assigned to the theoretical maximum value of the parameter, and if a threshold of the driver input is exceeded in an upper value range, a dynamic gauging is carried out such that the maximum displacement of the moveable control element is assigned to an actually recallable value of the parameter.

Abstract: A method for operating a drivetrain of a motor vehicle including a hybrid drive with a combustion engine and an electric motor. A transmission is arranged between the hybrid drive and a drive output and a clutch is arranged between the combustion engine and the electric motor so that, if a failure occurs in the drivetrain, especially in a transmission control device of the transmission, a gear corresponding to an emergency gear is engaged or remains engaged in the transmission. When the emergency gear is engaged, the motor vehicle is in motion and the engine speed falls below a defined value, the clutch arranged between the combustion engine and the electric motor disengages.

Abstract: A method of using a torque converter bypass clutch to launch a vehicle, mitigate transient vibration, and mitigate vehicle natural frequency harshness. The method uses the torque converter when the bypass clutch power capacity is approaching its limit, when the vehicle load is high, or the vehicle is on a grade, where normally the bypass clutch would launch the vehicle.

Abstract: A method of controlling an automatic transmission of a motor vehicle having clutches controlled by an electronic control unit. A transmission rotational speed in an initial transmission stage is determined. If a first transmission shifting rotational speed is reached, the transmission is shifted from the initial transmission stage to a target transmission stage. A target transmission rotational speed of the target transmission stage is then ascertained. A difference is next ascertained between the target transmission rotational speed and a second shifting transmission rotational speed. An initial counter value, of a counter, is determined, which depends on the transmission rotational speed difference. The counter is next caused to carry out counting, from the initial counter value, as time progresses. If and when the counter value reaches zero, the transmission is shifted from the target transmission stage toward the initial transmission stage.

Abstract: A method for the control of an automatic transmission during a change of ratio procedure, wherein the synchronous speed of rotation (SD) for the new transmission gear-stage lies under the no-load speed of rotation (LD) of a drive motor which can be connected to the transmission and wherein a gear-stage engagement actuator for the engagement of a new transmission gear-stage is then activated, when the transmission input speed of rotation (GED) has reached a predetermined speed of rotation window (F), which window also encompasses the synchronous speed of rotation (SD). In order to make such a shifting method more comfortable than previously, the invented method deviates from that procedure based on downshifting, which has been customary up to this time and rather proceeds in a upshifting mode.

Abstract: In a hybrid-drive electric vehicle, upon request of gear shifting of a transmission (2), a clutch (3) is first disconnected and the transmission (2) is set to a neutral position. The rotating electric generator 4 is then operated in a motor mode or a power generating mode so that a rotational speed of an input shaft of the transmission (2) reaches a region of a synchronizing rotational speed in accordance with a requested gear position. When the rotational speed of the input shaft of the transmission (2) reaches the region of the synchronizing rotational speed, the gear position of the transmission (2) is changed over from the neutral position to the requested gear position. Thus the rotation synchronizing time for the gear shifting in the transmission (2) is reduced, making it possible to perform the gear shifting for a short period of time.

Abstract: A lock-up clutch control device which controls a lock-up clutch (6) provided in a torque converter (5) interposed between an engine (3) and a transmission (4) used with a vehicle, is disclosed. The lock-up clutch control device has a differential pressure generating device (7,8), a vehicle speed sensor (13), a throttle valve opening sensor (14), an transmission input shaft rotation speed sensor (16), engine torque detection means (2), and a controller (1). The controller (1) determines, based on the detected vehicle speed (VSP) and the detected throttle valve opening (TVO), whether or not a control region of a torque converter is a converter region wherein control is performed to disengage the lock-up clutch.

Abstract: A shift control for an electrically variable transmission shifts between modes through a neutral mode wherein the output is decoupled from the transmission. Normally, shifts between modes are accomplished synchronously through a duration of fixed-ratio operation. Extreme driving conditions may invoke shifts through neutral mode. Ratio violations characterized by one mode being active in a preferred input/output ratio range for another mode are handled by a shift through neutral. Similarly, rapid acceleration and deceleration conditions likely to result in undesirable engine speeds if synchronous shifting is employed are handled by a shift through neutral.

Abstract: A method is described for operating an agricultural vehicle to reduce the time taken for rotating components of the crop processing machinery driven by the vehicle engine to reach a standstill. The method comprises the steps of sensing when a signal is generated by the vehicle operator to disengage the drive from the engine to the rotating components, reducing the engine speed in response to the sensed signal to a minimum value below a steady idling speed of the engine, disengaging the drive to the rotating components after the engine speed has reached the minimum value, and increasing the engine speed to a value equal to or greater than the steady idling speed after the disengagement of the drive to the rotating components.

Abstract: In shift control apparatus and method for an automatic transmission in which an engine speed is inputted, and a shift change in a shift stage of the automatic transmission is performed to make a gear shift, a shift revolution synchronization control in synchronization with the engine speed is performed and, in a case where the gear shift is made under a driving state in which there is a possibility of an occurrence of a shift shock, an engagement section which performs a power transmission under a presently selected shift stage is gradually released and another engagement section which enables a power transmission through the next selection scheduled shift stage is gradually engaged without an execution of the shift revolution synchronization control.

Abstract: A control apparatus for controlling a stepped automatic transmission of a vehicle having an output shaft and an input shaft which is to be connected to an engine of the vehicle through a clutch while a shifting action is being effected in the transmission. The control apparatus includes a torque vibration restrainer operable, upon completion of the shifting action in the transmission, to restrain a torque vibration which is generated in a power transmitting path of the vehicle. The torque vibration restrainer applies an inverted-phase torque vibration which is inverted in phase with respect to the generated torque vibration, to the power transmitting path, and/or place the clutch in its slipping state or released state, for restraining the generated torque vibration.

Abstract: A starting clutch control device includes a starting clutch disposed between an engine and a transmission installed to a vehicle. A torque coefficient setting section sets a torque coefficient based on a clutch speed ratio of the starting clutch and a throttle opening of the engine. A torque coefficient correction section increases the torque coefficient by a torque coefficient correction amount, increasing the torque coefficient by a progressively larger torque coefficient correction amount as the throttle opening increases, in order to increase the torque coefficient within a region of smaller clutch speed ratios (e.g., clutch speed ratios less than approximately 0.5). A hydraulic pressure control section controls hydraulic pressure supplied to the starting clutch based on the torque coefficient and the rotational speed of the engine.

Abstract: If a user presses a clutch pedal to perform gear-shifting operation while a vehicle is traveling, a clutch disc, which has been engaged with a flywheel rotating with an engine, is brought to partial clutch engagement and slides on an end surface of the flywheel to generate friction. Thus, a first phenomenon in which a decreasing rate of the engine rotation speed rapidly increases occurs. Then, a second phenomenon in which the clutch disc is completely disengaged from the flywheel to eliminate the friction and the decreasing rate of the engine rotation speed returns to an original state occurs. If the first and second phenomena are detected successively when neither an engine side nor a power transmission system side transmits power for varying an engine rotation speed, it is determined that the clutch disc is disengaged.

Abstract: A control system for a vehicle includes an engine switch control unit for switching the operating condition of the engine between the all-cylinder operating condition and the partial-cylinder operating condition, a failure determining unit for determining the failure of the lockup clutch control device, and a coupling capacity change inhibiting unit for inhibiting a change in coupling capacity of the lockup clutch accompanied by the switch control of the operating condition of the engine by the engine switch control unit during the failure determination by the failure determining unit.

Abstract: An apparatus is provided for controlling a joint force of a friction-joint component placed in a torque transmitting mechanism (e.g., transmission) mounted on a vehicle. The friction-joint component is connected to a drive source. The apparatus comprises a guideline producing unit, joint force controlling unit, and drive force controlling unit. The guideline producing unit produces a first target operation guideline for the torque transmitting mechanism and a second target operation guideline for the drive source. The first target operation guideline includes a transmitted torque capacity of the torque transmitting mechanism. The joint force controlling unit controls the joint force based on the first target operation guideline. The controlling unit includes a unit setting a value to the joint force depending on the information regulating the transmitted torque capacity. The drive force controlling unit controls a drive force of the drive source based on the second target operation guideline.

Abstract: A method and an arrangement automatically restarts a drive unit (1) when there is an unintended stalling of the drive unit (1). In the case of stalling, checks are made as to whether the drive unit (1) was already in a steady-state condition directly before the stalling, as to whether the stalling took place because of an operator input, especially at an input unit (5) and as to whether a force-tight connection between the drive unit (1) and a transmission (25 or 80) is present. A restart of the drive unit (1) is automatically initiated when: the drive unit (1) was already in a steady-state condition directly before the stalling; when the stalling took place in a departure from the operator input; and, when the force-tight connection between the transmission (25 or 80) and the drive unit (1) is interrupted.

Abstract: An apparatus for clutch braking in a multi-speed transmission comprising a prime mover, a transmission system, an output shaft and a torque converter. The transmission comprises a first stage and a second stage wherein the first stage comprises at least two range clutches and the second stage comprises at least two direction clutches. The range and direction clutches are slipped, locked and/or engaged to brake the system.

Abstract: A method of controlling a drive train of a motor vehicle having an engine, wheels, a wheel slip control system, and an automatic transmission having a clutch, the clutch capable of being opened and closed, wherein the automatic transmission is controlled based upon signals generated by the wheel slip control system.

Abstract: Systems and methods for controlling shift and throttle of an electronically controlled power train are disclosed. The system includes a throttle or shift controller having an operating range. An hydraulic slave is in fluid communication with the controller such that a movement of the controller within its operating range causes a flow or displacement of fluid between the controller and the hydraulic slave. The hydraulic slave has a shaft that rotates in response to the fluid flow between the controller and the hydraulic slave. The shaft is adapted to be coupled to a position sensor such that rotation of the shaft causes the position sensor to produce electrical throttle control signals that represent the movement of the controller within its operating range. The electrical signals can be adapted to cause the power train to set an engine throttle and a transmission shift position according to a current position of the controller within its operating range.

Abstract: The comfort level gear shift motor vehicle with an automated gear-shifting transmission is determined by shift parameters, which are dependent on driving parameters and on a shift program mode. The shift program mode identified through a characteristic parameter, which can vary a range of parameter values corresponding to a range of shift program modes. The method has the steps of detecting current values the driving parameters, detecting a current value of the characteristic parameter, determining respective minimum and maximum values that each of said shift parameters can assume within the range of characteristic parameter values as a function of the current driving parameter values, calculating actual shift parameter values as intermediate values between said maximum and minimum values for each of said shift parameters based on said current value of the characteristic parameter, and performing the gear shift with the actual shift parameter values.

Abstract: When a deceleration slip executing minimum gear stage is not established in a state of continuously executing a deceleration slip control at a target slip amount, it is judged whether or not an input shaft rotational speed of a transmission becomes a down shift judging rotational speed. When it becomes equal to or less than a predetermined down shift judging rotational speed, a down shift is executed, and a clutch pressure is controlled such that an engine rotational speed becomes a target engine rotational speed.

Abstract: A rotational driving force from an engine E in a fuel-supply termination control is transmitted through a continuously variable transmission CVT, and this transmission of the rotational driving force is controlled by the engagement of a starting clutch 5. In this arrangement, a control system terminates the fuel supply to the engine at the elapse of a predetermined time from the starting of a deceleration of the vehicle. When the control system detects that the throttle of the engine has closed, it reduces the engaging force of the starting clutch 5 to disengage the clutch into a pre-engagement condition. Thereafter, when the fuel supply to the engine is terminated, the engaging force is gradually increased to bring the starting clutch 5 gradually into engagement.

Abstract: A system is described for minimizing engine torque disturbances that would otherwise cause degraded drive feel by a vehicle driver. The system utilizes multiple torque transmission paths of a transaxle unit mounted to the engine. The system manipulates the torque transmitted by adjusting the clutches of multiple torque transmission paths so that the torque disturbance in the engine results in relatively constant vehicle drive torque. In one example, a potential torque increase at high speed and low airflow that may be cause using electronically actuated valves is compensated for using multiple paths of the transmission. In this way, relatively constant output torque can be maintained.

Abstract: The invention relates to a method for calculating a modification to the predetermined amount of torque needed to provide an urge to move sensation for a vehicle, the modification to take account of the weight at which and gradient on which the vehicle is operating and then commanding the engine to generate said modified torque and to transmit the modified urge torque to a clutch device to provide the urge to move according to the current operating conditions.

Abstract: A method of controlling a drive train of a motor vehicle having an engine, wheels, a wheel slip control system, and an automatic transmission having a clutch, the clutch capable of being opened and closed, wherein the automatic transmission is controlled based upon signals generated by the wheel slip control system.

Abstract: A computer-implemented method for initiating forward motion in a vehicle equipped with a manual transmission. The method includes the steps of providing a sensor for determining clutch status; providing a sensor for determining when a transmission of a vehicle is in first gear; providing a throttle actuator calibrated to raise engine revolutions per minute from idle to a predetermined elevated level upon receipt of a throttle-up signal; and providing a control unit to receive inputs from the clutch and gear status sensors. The control unit is programmed to deliver the throttle-up signal to the throttle actuator when the sensor of clutch status indicates that a change in clutch status from engaged to non-engaged, and the gear sensor indicates that the vehicle is in first gear.

Abstract: The invention is directed to a method and an arrangement for automatically restarting a drive unit (1) including an internal combustion engine of a motor vehicle. The method and arrangement provides for an automatic restart when there is an unintended stalling of the drive unit (1). In the case of a stalling of the drive unit (1), a check is made as to whether the drive unit (1) was already in a steady-state condition directly before the stalling. Furthermore, a check is made as to whether the stalling of the drive unit (1) took place because of an operator input, especially at an input unit (5). In addition, a check is made as to whether a force-tight connection between the drive unit (1) and a transmission (25 or 80) is present.

Abstract: A decelerator control system includes a first control member, a machine control device, an engine, at least one brake, and a transmission. The first control member is manually moveable and is adapted to produce a first operator control signal. The machine control device is adapted to receive the first operator control signal and responsively produce an engine control signal, a brake control signal, and a transmission control signal. The engine is adapted to receive the engine control signal and responsively control the speed of the engine. The brake is adapted to receive the brake control signal and responsively control an engagement of the brake. The transmission is adapted to receive the transmission control signal and responsively control an engagement of the transmission.

Abstract: A control apparatus for a synchromesh automatic transmission (3) for automatically changing over a plurality of speed gear stages from one to another in an internal combustion engine (1), which apparatus is capable of suppressing occurrence of rapid deceleration of the engine, engine blowup or like problems even when the accelerator pedal is manipulated during a period in which the throttle valve is being closed. The control apparatus includes an electromagnetic clutch (2), an accelerator pedal position sensor (13), an engine rotation speed sensor (15), and a control unit (4) arranged such that upon decision of start of upshift operation, a closing speed of an electronically controlled throttle valve (11) is arithmetically determined by the control unit (4) on the basis of a data map prepared in advance with opening degree of the throttle valve (11) being controlled in response to a command value issued by the control unit (4).

Abstract: A device for controlling an engine equipped with a synchronous mesh-type automatic transmission which decreases shock at the time of changing the speed, and improves the response and drive feeling at the time of changing the speed, including a controller that controls a throttle actuator and the automatic transmission, sets a synchronizing rotational speed of the engine rotational speed relative to the clutch when the clutch is disconnected at the time of changing the speed, fixes the throttle opening degree so that the engine rotational speed converges to the synchronizing rotational speed, gradually returns the throttle opening degree to an opening degree that corresponds to the synchronizing rotational speed when a difference between the engine rotational speed and the synchronizing rotational speed has converged to lie within a first predetermined range, and connects the clutch again when the direction of change of the engine rotational speed is inverted.

Abstract: An automatic transmission system has a switching mechanism for switching a plurality of shift gears and a sub-clutch by which transfer torque is controlled while being transferred from an input shaft to an output shaft. An actual deceleration speed is calculated based on an engine speed. Calculated next, based on an engine torque, is a target deceleration speed at which an output torque generated during upshifting is almost equal to an output torque generated after the upshifting. The transfer torque is controlled by feedback control so that the actual deceleration speed reaches the target deceleration speed.

Abstract: A control system/method controls a vehicular automated transmission system so as to overcome a tooth butt condition. The automated transmission system including an internal combustion engine having an engine output member, a multiple speed change gear transmission having an input shaft, a centrifugal friction clutch for drivingly connecting said engine output member to said input shaft, a throttle responsive to manually requesting of a degree of engine fueling, and a system controller. The system controller varies the engine speed to encourage gear engagement upon sensing the tooth butt condition.

Abstract: A control system/method for controlling a vehicle drivetrain (10) including an engine (18), a transmission (12) and, a centrifugal clutch (20) for drivingly coupling the engine output (136) to the transmission input shaft (28) during vehicle launch. A system controller (50) issues command output signals (56) for controlling engine speed (ES) on a closed loop basis.

Abstract: The power train of a motor vehicle employs an electronic control unit which selects the extent of engagement of the friction clutch between the engine and the transmission by way of an electronic or fluid-operated actuator. The throttle valve for the engine is adjustable by the control unit and/or by the accelerator pedal to ensure predictable starting of the motor vehicle from standstill on a road surface having a pronounced slope and/or when the motor vehicle carries a heavy load.

Abstract: A control apparatus for a drive system, in which a power source is activated to output a torque by an energy fed from an energy source so that the torque is transmitted to rotary members through a torque transmission element having a variable transmission torque capacity. The stop of the power source due to the exhaustion of energy is predicted to increase the transmission torque capacity of the torque transmission element.

Abstract: The extent of engagement of an automatically adjustable friction clutch in the power train of a motor vehicle, wherein the clutch receives torque from a rotary output element of an engine and transmits torque to the rotary input element of a transmission, is determined by an electronic control unit in conjunction with an actuator which is responsive to signals from the control unit. Under normal circumstances, the adjustment of the clutch is selected on the basis of control signals which depend upon the actual RPM of the output element and the RPM of the input element. When the actual RPM of the output element departs from a desired RPM, the control signal is altered to reduce the rate of torque transmission by the clutch upon a determination that the actual RPM is below the desired RPM, and to increase the rate of torque transmission by the clutch when the actual RPM exceeds the desired RPM.

Abstract: A method of controlling a drive train of a motor vehicle having an engine, wheels, a wheel slip control system, and an automatic transmission having a clutch, the clutch capable of being opened and closed, wherein the automatic transmission is controlled based upon signals generated by the wheel slip control system.

Abstract: An apparatus and method of operating an adaptive drive system of a motor vehicle which reduces drive line wear, improves safety margins and permits weight reduction in drive line components activates a clutch between a primary and secondary drive line when the vehicle is determined to be heavily loaded. The method steps include sensing the position of a throttle position sensor, sensing the instantaneous speed of a motor vehicle and computing instantaneous acceleration, determining whether the ratio of vehicle acceleration to throttle position is less than predetermined threshold value and engaging a transfer case clutch to transfer drive torque from a primary drive line to a secondary drive line. Operation of this method is transparent to the driver inasmuch as the clutch is activated when the vehicle is heavily loaded as determined by the throttle position to acceleration ratio.