Abstract: A powertrain includes a drive motor, a gear mechanism, a left half shaft, a right half shaft, a differential, a clutch, and a clutch control component, where an output shaft of the drive motor is connected to the gear mechanism, and the gear mechanism is mounted on the differential by using a bearing.

Abstract: An axle assembly having an input shaft, an output shaft, and an interaxle differential unit. The interaxle differential unit includes first and second side gears, a case, and a pinion gear that is rotatably disposed on a pinion pin. The case extends from the input shaft. The pinion pin extends from the case and is spaced apart from the input shaft.

Abstract: A front axle assembly with an axle housing that has first and second housing halves that each include a main housing portion, a tubular portion and a steering yoke. The main housing portion defines a cavity that houses at least a portion of a speed differentiation mechanism. The tubular portions are fixedly coupled to an associated one of the main housing portions and extend between the main housing portion and an associated one of the steering yokes. Each steering yoke is fixedly coupled to an associated tubular portion. An annular joint structure is formed where the first and second first housing halves are coupled to one another. The annular joint structure is formed about the rotary axis such that one of the first and second housing halves is inserted into the other one of the first and second housing halves along an insertion axis that is coincident with the rotary axis.

Abstract: A rear drive unit (RDU) for a vehicle includes a shift collar, a sleeve disposed around the shift collar, a planetary gear set, a differential including a side gear, and a locking plate configured to engage the side gear. The sleeve is configured to move the shift collar between a first position and a second position. The planetary gear set includes a sun gear and at least one planetary gear engaged with the sun gear. The sun gear is configured to engage the shift collar in the second position. The at least one planetary gear includes a pin extending through an entire length of the at least one planetary gear. The shift collar is configured to exert a force upon the locking plate via the pin to move the locking plate into engagement with the side gear in a third position.

Abstract: A vehicle control apparatus including a driving force generation unit, a driving force distribution mechanism distributing a driving force from the driving force generation unit to a front wheel and a rear wheel, and an electronic control unit having a microprocessor and a memory. The microprocessor is configured to perform: determining whether a mode switching instruction from self-drive mode enabling a self-drive function to manual drive mode disabling the self-drive function has been input; and controlling the driving force distribution mechanism so that a driving force distribution rate of rear wheel driving force relative to front wheel driving force is a first distribution rate during driving in the self-drive mode, and thereafter so that the driving force distribution rate is a second distribution rate greater than the first distribution rate when it is determined that the mode switching instruction has been input.

Abstract: A power train for a vehicle may include a differential case; a differential ring gear aligned to be concentric to the differential case, and provided in a relatively rotatable state therebetween; and a connection/disconnection mechanism provided to connect or disconnect the differential ring gear and the differential case in a state where power is transferred thereto.

Abstract: A transfer case with an actuator for operating a two-speed transmission (i.e., range mechanism) and a clutch (i.e., mode mechanism). The actuator employs a motor-driven cam structure that coordinates the movement of a first fork, which is associated with the range mechanism, and a second fork that is associated with the mode mechanism. A resilient coupling is employed to provide compliance between the motor and the cam structure in the event that tooth-on-tooth contact inhibits the range mechanism from changing from a high-range mode and a low range mode or tooth-on-tooth contact inhibits the mode mechanism from changing between a two-wheel drive mode and a four-wheel drive mode. A sensor target and sensor are employed to identify the rotational positioning of the cam structure placement, which is indicative of the modes in which the transmission and the clutch are operating.

Abstract: A vehicle driveline component having a housing, a shaft received in the housing, a lubricant pathway coupled to the shaft for rotation therewith, a sleeve disposed coaxially about the lubricant pathway, and a fluid feed conduit coupled to the component housing. The lubricant pathway is disposed helically about an exterior surface of the shaft. The sleeve has a feed port. The fluid feed conduit having an outlet that is in fluid communication with the feed port. Lubricant in the lubricant pathway that has been discharged from the outlet of the fluid feed conduit travels in a predetermined axial direction along the rotary axis of the shaft when the shaft rotates about the rotary axis in a predetermined rotational direction.

Abstract: An arrangement (100) for specifying the pressure (64), produced by a pump (30) driven by an electric motor (31), includes a processor (116) which derives a target pressure value (62, 118) from an internal torque value (114) and a loss torque (108). The arrangement (100) further derives (112) the internal torque value (114) from a motor current value (110) and a motor constant ke.

Abstract: A transmission to transfer case adaptor kit, having a transfer case to convert a two-wheel drive production truck to four-wheel drive enabling a drivetrain that allows all four wheels of the truck to receive torque from an engine of the truck, whereby the truck has a transmission system and is retrofitted with a front axle adaptor kit, and a transfer case parking brake system adaptor kit and support mount.

Abstract: A front axle adaptor kit, having a front differential assembly, first and second shock absorber brackets, a spring support bracket, a track-bar bracket, and a dampener bracket to convert a two-wheel drive production truck to four-wheel drive enabling a drivetrain that allows all four wheels of the truck to receive torque from an engine of the truck. The truck has a transmission system and is retrofitted with a transmission to transfer case adaptor kit, and a transfer case parking brake system adaptor kit and support mount.

Abstract: An axle drive mechanism includes a driving toothed wheel, a drive mechanism housing, a differential cage, a differential gear, a first and a second output shaft, and at least one shiftable torque transmission device. The at least one shiftable torque transmission is disposed between the driving toothed wheel and the first output shaft and includes a torque transmission region. The torque transmission region is at least partially disposed between said differential cage bearings in the axial direction.

Abstract: A transfer case parking brake system adaptor kit and support mount to convert a two-wheel drive production truck to four-wheel drive enabling a drivetrain that allows all four wheels of the truck to receive torque from an engine of the truck, whereby the truck has a transmission system and is retrofitted with a front axle adaptor kit, and a transmission to transfer case adaptor kit.

Abstract: A differential lock mechanism includes a shift member and a shift collar that is moveable by the shift member between an engaged position with a differential assembly and a disengaged position. A pneumatic control provides a first pneumatic signal to move the shift collar into the engaged position and provides a second pneumatic signal to return the shift collar to the disengaged position.

Abstract: A transmission power switch device assembled with rotary shaft has a simplified structure and provides power transmission and switching effect. The transmission power switch device includes a rotary shaft connected with a power source. On the rotary shaft are disposed a first drive mechanism, a second drive mechanism and a brake device rotatable with the rotary shaft. The brake device is movable on the rotary shaft to selectively brake the first drive mechanism or the second drive mechanism so as to transmit power to an output shaft.

Abstract: A differential mechanism regulating device which is mechanically connected to two manipulators is miniaturized. When a first cable and a second cable are pulled, a collecting member moves its position. As a result of this movement, the collecting member tilts a portion of an arm by way of a rod. As a result, a differential lock is released. The operation of the first cable and the operation of the second cable can be merged by the collecting member, and it is sufficient to connect only a collecting transmission member to the arm. The connection between the arm and the collecting transmission member can be simplified thus realizing the miniaturization of the differential mechanism.

Abstract: A vehicle is described having plural modes of operation for the front and rear differential and whereupon start-up of the vehicle, the front and rear differentials are opened to their most open position.

Abstract: A vehicle can be operated in a first drive mode in which a front differential is set to a non-driven state and a rear differential is set to a differential state, a second drive mode in which the front differential is set to a non-driven state and the rear differential is set to a differential locked state, a third drive mode in which the front differential is set to a differential state and the rear differential is set to a differential locked state, and a fourth drive mode in which the front differential is set to a differential locked state and the rear differential is set to a differential locked state. Transition is allowed only between adjacent drive modes.

Abstract: A differential action railroad car wheelset axle has two individual stub axles, each having one or more annular rings or grooves on the interior ends, with the interior ends of the individual stub axles being rotatably mounted within a multi-piece sleeve assembly. The axle assembly has provision for safety pins to prevent independent rotation during installation in the railcar truck frame and also a device to permit relocking or unlocking the independent axle rotation after the original safety pins have been removed. Dry lubricant coatings eliminate the need for periodic liquid lubrication or maintenance. The differential action of the wheelset reduces the horsepower requirement by approximately 30 percent while also reducing the maintenance requirements for both wheels and track in locations where horizontal curves are predominant.

Abstract: A differential assembly includes an axle, a differential, a differential lock, a blocking member, and a pump. The differential is coupled with the axle and configured to facilitate operation of the axle at an axle speed. The differential lock is associated with the differential and movable between a locked position and an unlocked position. The blocking member is associated with the differential lock and is movable between a blocking position and a non-blocking position. When the blocking member is in the blocking position, the differential lock is inhibited from moving to the locked position. The pump includes an outlet in fluid communication with the blocking member. The pump is operably coupled with the axle and is configured to facilitate movement of the blocking member into the blocking position when the axle speed is above a threshold speed. Vehicles including a differential assembly are also provided.

Abstract: A vehicle drive control for a wheeled vehicle including a first motor generator, and a second motor generator. A planetary gear set includes a first rotating element connected to the first motor generator, a second rotating element connected to the second motor generator, and a third rotating element connected to a drive wheel. A rotation control mechanism selectively restricts rotation of one of the first and second rotating elements of the planetary gear set to establish a fixed speed ratio mode, and releases the one of the first and second rotating elements to establish a variable speed ratio mode. A control unit is configured to control each operating state of the rotation control mechanism, the first motor generator, and the second motor generator, and configured to establish the variable speed ratio mode when a slip state of the drive wheel is detected in the fixed speed ratio mode.

Abstract: A device and a method for engaging and disengaging a longitudinal differential (10) disposed between a forward wheelshaft (4) and a rear wheelshaft (5) of an articulated vehicle (1) which has a front element (2) and a rear element (3) pivotable about a steering linkage (6) disposed between them and which comprises a distribution box (9) which supplies power from an engine (7) to the forward wheelshaft (4) in the front element (2) via a first shaft (11) and to the near wheelshaft (5) in the rear element (3) via a second shaft (12), wherein the longitudinal differential (10) is disposed between the first shaft (11) and the second shaft (12), whereby a steering angle v formed between the front element (2) and the rear element (3) is detected by a detection means (25a) so arranged that the detection means (25a) causes a differential brake (20) for the longitudinal differential (10) to be kept locked, or braked, when the detection means (25a) detects a steering angle v which is smaller than a predetermined steerin

Abstract: A control device for a four-wheel drive vehicle, including: a yaw moment control unit for selecting and applying to a wheel based on a driving state a braking force to generate vehicular yaw moment; a driving force control unit for identifying and reducing excess driving force based on the driving state; a limited slip differential control unit for limiting a front wheel differential; a front/rear driving force distribution control unit for controlling engagement torque of a clutch unit which varies front/rear torque distribution via a center differential; and a switch unit for selecting an operation/non-operation of the driving force control unit, wherein the front/rear driving force distribution control unit sets the engagement torque at a greater value when the yaw moment control unit operates while the driving force control unit is non-operating, than when the yaw moment control operates while the driving force control unit is operating.

Abstract: In a four-wheel drive motor vehicle with a primary drive axle and a secondary drive axle, at least one secondary drive axle coupling of the limited slip type is provided in the powertrain between the engine of the vehicle and the secondary drive axle. A primary drive axle coupling of the limited slip type is provided for the primary drive axle.

Abstract: A drive switching lever device for a vehicle for a vehicle in which a single control lever can operate both two-wheel-drive/four-wheel drive switching means and a differential lock on/off switching mechanism includes a bell crank swingably supported by a vehicle body side. A pull rod adapted to operate a switching lever of a two-wheel-drive/four-wheel-drive switching means is connected to a lever bracket and a control cable adapted to operate a switching lever of a differential lock on/off switching mechanism is connected to the bell crank. When a control lever is swung independently of the lever bracket, the bell crank is swung in engagement with the shaft portion of the control lever. The resulting configuration provides flexibility for the layout of the linkage between the control lever and the operating portion of each switching mechanism.

Abstract: In an all-wheel drive train for a motor vehicle wherein the drive torque of the engine of the motor vehicle is transmitted from the transmission output shaft partially to the rear axle and partially to the front axle via an offset transmission structure and a laterally arranged drive shaft extending from the offset transmission structure past the transmission to the front axle of the motor vehicle extends from the offset transmission forwardly at a certain opening angle in close proximity to the transmission structure which narrows down toward the rear so that the rear end of the lateral drive shaft is relatively close to the center axis of the transmission.

Abstract: An electric drive unit for a vehicle includes an electric motor, two output shafts, a first speed reduction planetary gearset driven by the motor, a second speed reduction gearset driven by an output of the first gearset, and a compound planetary differential gearset including an input driveably connected to the output of the second gearset, a first differential output driveably connected to the first output shaft, and a second differential output driveably connected to the second output shaft.

Abstract: An off-road vehicle has front and rear wheels. An engine unit powers the wheels. The engine unit has an output shaft. A front differential is coupled with the front wheels. The front differential has a front input shaft. A front drive connects the output shaft and the front input shaft with each other. The front differential can operate in one of three modes: an unlocked mode, a locked mode and a disabled mode. A rear differential is coupled with the rear wheels. The rear differential mechanism has a rear input shaft. A rear drive connects the output shaft and the rear input shaft. The rear differential can operated in at least two modes: an unlocked mode and a locked mode. In one embodiment, the front differential is allowed to be locked only when the rear differential is locked.

Abstract: A transfer arrangement for a four-wheel drive vehicle having an input shaft, a transmission, and a center differential. The transmission includes a first gear attached to the input shaft, a first counter gear attached to a countershaft in parallel with the input shaft to receive the rotation of the first gear, a second counter gear fixed to the countershaft and rotating therewith, and a second gear aligned with the input shaft and rotatably supported along the input shaft to receive the rotation of the second counter gear. High speed-side and low speed-side output parts are attached to the first and second gears respectively. The center differential is disposed between the high speed-side and low speed-side output parts. An engaging device disposed adjacent the center differential selectively engages with the high speed-side and low speed-side output parts.

Abstract: A dry friction device, in particular a clutch friction wheel or a brake disc for a motor vehicle, includes at least one friction liner made of a dry friction material containing reinforcing fibers. Such a friction material comprises a mat of fibers impregnated with a thermosetting resin, the fibers having a length of at least 40 mm. Glass fibers are preferably incorporated into the mat.

Abstract: A driving force transmitting device for a vehicle includes a drive mode-shifting mechanism which is disposed in the final drive gear-set of a vehicle. The drive mode-shifting mechanism includes a first rotating member, a second rotating member, a third rotating member, and a movable member. The movable member is movable between a first position in which the first and second rotating members are disconnected to effect the two-wheel-drive mode, a second position in which the first and second rotating members are connected to effect differential-free four-wheel-drive mode, and a third position in which the second and third rotating members are connected to effect the differential-lock four-wheel-drive mode.

Abstract: A transmission structure of a gearbox of an electrically actuated car includes two front wheels, two rear wheels, and two gearboxes, wherein one gearbox is mounted between the two front wheels, and the other gearbox is mounted between the rear wheels. The transmission structure also includes a motor mounted between the two gearboxes. The motor has a power shaft having two distal ends each connected to a differential gear of each of the two gearboxes by means of a coupler, so as to form a four-wheel transmission mechanism.

Abstract: A differential limiting mechanism produces a changeable differential limiting torque. A differential limiting mechanism operating lever is disposed so as to be operated and turned by a hand gripping a handgrip attached to a handlebar. The operating lever is interlocked with the differential limiting mechanism so that the differential limiting torque varies according to an angle through which the operating lever is turned. A lever stopping mechanism stops the operating lever at an angular position for producing a predetermined maximum differential limiting torque.

Abstract: A wheel driving system is capable of varying differential limiting torque applied to a differential included in an all-terrain vehicle according to the difference between loads respectively applied to the right and the left wheel of the vehicle, which varies depending on the traveling condition or turning condition of the vehicle. Right and left wheels are connected through a differential gear mechanism (30) having a differential case (46) and held in a reduction gear case (13), an input pinion (22) and a drive shaft to an engine. The differential case (46) and a differential gear shaft (36) connected to the wheel are interlocked by a wet multiple-disk differential limiting mechanism (31) having a friction clutch mechanism immersed in oil. The multiple-disk differential limiting mechanism (31) is operated by a multiple-disk differential limiting mechanism operating mechanism to vary differential limiting torque.

Abstract: A forward and aft torque distribution system and a method of controlling forward and aft torque distribution for a four-wheel vehicle having an electronically controlled clutch to control split of drive torque to be transferred to front and rear wheels are disclosed. A 4WD controller is responsive to mode selection signals from a mode changeover switch and a vehicle speed signal delivered from a vehicle speed sensor, and has control modes involving at least a LOCK mode and an AUTO mode. When the vehicle speed becomes less than a vehicle's halt discriminative vehicle speed indicative of a vehicle's halt state during the LOCK mode, the controller allows the electronically controlled clutch to be released.

Abstract: In a working vehicle such as an agricultural tractor, a front wheel change speed device for transmitting drive to front wheels includes an equal speed clutch for driving the front wheels substantially at the same speed as rear wheels, and an accelerating clutch for driving the front wheels substantially at a higher speed than the rear wheels. In the front wheel change speed device of this invention, the equal speed clutch and accelerating clutch are arranged coaxially. The front wheel change speed device further includes a shift member axially shiftable for selectively operating the equal speed clutch and accelerating clutch, and an actuator for axially shifting the shift member.

Abstract: A system for monitoring spinout conditions in a heavy vehicle driveline provides the ability to monitor the manner in which a driver operates a vehicle. For example, spin out conditions that occur with greater frequency than is normally expected indicates an inappropriate manner of operating the vehicle. Similarly, spinouts that have relatively excessive duration indicate inappropriate vehicle operation. The system includes a sensor device for detecting a spinout condition and a detector for detecting whether a differential lock has been engaged by the vehicle operator. An electronic controller gathers information from the sensor device and the detector and records information regarding each spinout including the frequency and duration. This information is then later provided to a service technician to determine whether the vehicle warranty provisions have been violated.

Abstract: A first power train (T1) for driving a pair of front drive wheels (Wf1, Wf2) comprises a transmission (4) connected to an engine (2) and a front drive train (41f) connected to the drive wheels, the front drive train including a final reduction gear (43), and a second power train (T2) for driving a pair of rear drive wheels (Wr1, Wr2) comprises a rear transfer train (11) branched from the first power train, between the transmission and the front drive train, and a rear drive train (41r) connected to the rear drive wheels.

Abstract: In a four wheel drive system for an automotive vehicle, a detected value .DELTA.V.sub.W of difference of rotating speed between the front and rear wheels is compared with a threshold .DELTA.V.sub.W0 determined in accordance with a pseudo vehicle speed V.sub.FF (S116, S213). As a result of this, when a determination is made that the pseudo vehicle speed V.sub.FF is in a directly connecting four wheel drive condition inhibiting range, a directly connecting four wheel drive condition inhibiting signal S.sub.N is sent out (S121), so that a front wheel side torque distribution instruction value T.sub.2 is determined as a value preventing the directly connecting four wheel drive condition. Thereby, in case of using of the different diameter wheel, a deterioration of stability and an increase of load of power train system caused by the directly connecting four wheel drive condition can be prevented.

Abstract: A transfer case for a four-wheel drive vehicle having a planetary gear assembly which integrates a gear reduction unit and an interaxle differential into a common assembly. A synchronized range clutch is operably associated with the input to the planetary gear assembly and can be selectively shifted on-the-fly for establishing high-range and low-range speed ratios. A biasing clutch is operably associated with the output of the planetary gear assembly to automatically limit speed differentiation and bias the torque distribution between the outputs of the planetary gear assembly in response to excessive wheel slip.

Abstract: In a four wheel drive system for an automotive vehicle, a detected value .DELTA.V.sub.W of difference of rotating speed between the front and rear wheels is compared with a threshold .DELTA.V.sub.W0 determined in accordance with a pseudo vehicle speed V.sub.FF (S16, S213). As a result of this, when a determination is made that the pseudo vehicle speed V.sub.FF is in a directly connecting four wheel drive condition inhibiting range, a directly connecting four wheel drive condition inhibiting signal 8.sub.N is sent out (S121), so that a front wheel side torque distribution instruction value T.sub.2 is determined as a value preventing the directly connecting four wheel drive condition. Thereby, in a case where different diameter wheels are used, a deterioration of stability and an increase of load of power train system caused by the directly connecting four wheel drive condition can be prevented.

Abstract: A power transfer system for a four-wheel drive vehicle having a full-time transfer case with its input angled relative to its outputs by means of a constant velocity (CV) universal joint. More specifically, the transfer case input includes a first rotary member adapted to be rotatably driven about the rotary axis of the transmission output shaft, a second rotary member supported for rotation about a second rotary axis that is angled relative to the first rotary axis, and a CV joint interconnecting the first and second rotary members. The transfer case outputs include a pair of rotary output members supported for relative rotation about a common third rotary axis that is offset from the second rotary axis. A torque transfer arrangement is provided for transferring torque from the transfer case input to its outputs. The CV joint allows the transfer case to be angulated so that reduced departure angles are achieved with respect to the prop shaft connections.

Abstract: A transfer case for a four-wheel drive vehicle adapted to provide two- to four-wheel drive on-demand in the high range or four-wheel drive in the low range. The transfer case includes an input shaft coupled to the sun gear of a planetary gear set, a main drive shaft, a first output and a second output. Provided in fixed association with the main drive shaft is a viscous fluid coupling chamber, and associated with the chamber is a drive sprocket. A range clutch sleeve and locking clutch assembly is slidably disposed on the main drive shaft between the planetary gear set and the rotary member for selectively providing two- to four-wheel on-demand high range power, neutral, and four-wheel drive low range power. Inner and outer relatively rotational drum housings surround the aft end of the main drive shaft for defining an annular viscous fluid coupling chamber therebetween.

Abstract: A four-wheel drive vehicle control system has a differential mode control device which operates in at least a first mode, in which differential action of a differential is variably restricted between an unlocked state and a locked state according to driving conditions, and a second mode, in which the differential is forcibly locked. The first and second modes are manually selected by the driver.

Abstract: A power transmitting system for a vehicle includes a rotatable input shaft for introducing driving power into the system, a rotatable first output shaft for transmitting the driving power from the system, and a rotatable second output shaft for also transmitting the driving power from the system. A transmitting member is rotatably mounted on the first output shaft and for rotating the second output shaft, a clutch mechanism is disposed adjacent to the transmitting member and mounted on the first output shaft for engaging the transmitting member with the first output shaft. An actuator is provided for actuating the clutch mechanism. A compact power transmitting system can be obtained.

Abstract: A power transfer device having a center differential gear unit for use in a four-wheel drive vehicle of part time four-wheel drive type of the present invention comprises: an intermediate shaft which is rotatably provided around a rotary shaft, which rotary shaft is driven to transmit the driving power of an engine and connected with one of the output elements of the center differential gear unit, and which is detechably connected with the rotary shaft through the first clutch mechanism; and an output shaft which is rotatably provided around the intermediate shaft and detachably connected with the intermediate shaft through the second clutch mechanism having a synchro-mesh unit, wherein the transmission can be optionally changed over among the two-wheel drive state in which the center differential gear unit is locked, the four-wheel drive state in which the center differential gear unit is locked, and the four-wheel drive state in which the center differential gear is released, by moving the sleeve in the fir

Abstract: The present invention provides a motor vehicle cold shift assist system for selectively actuating an axle connecting mechanism to automatically connect the non-driven wheels to its associated axle drive mechanism immediately following synchronization for counteracting the inertial loading acting on the transfer case synchronizer clutch mechanism. The axle connecting mechanism is actuated prior to the transfer case being locked in the four-wheel drive mode. As such, the present invention substantially reduces the shift resistance and gear clash encountered upon the vehicle operator shifting into the four-wheel drive mode during cold weather conditions.

Abstract: The present invention provides a motor vehicle cold shift assist system for selectively and automatically connecting the non-driven wheels to its associated axle drive mechanism under certain operational and temperature conditions for counteracting the inertial loading acting on the transfer case synchronizer clutch mechanism. The present invention substantially reduces the shift resistance encountered upon the vehicle operator subsequently shifting into the four-wheel drive mode during cold weather conditions.

Abstract: To simplify propeller shaft supporting structure and to reduce propeller shaft vibration when a viscous coupling and a clutch mechanism are both provided on a propeller shaft of a 4WD vehicle, the power transmission apparatus comprises a housing rotatably supported to receive power; a differential gear disposed on one side of and within the housing; a viscous coupling disposed on the other side of and within the housing; and a clutch for transmitting power from the housing to the differential gear via the viscous coupling when engaged, and transmitting no power from the housing to the differential gear when disengaged.

Abstract: A four-wheel vehicle drive system, comprising an engine having an output shaft in a lateral direction of the vehicle, a power transmission gear unit including transmission input and output shafts having axes of rotation parallel with the engine output shaft, a final reduction gear rotatable about an axis parallel with the transmission input and output shafts, the transmission output shaft being in driving engagement with the final reduction gear, a gear housing rotatable with the final reduction gear, a main transaxle casing having enclosed therein the transmission gear unit, final reduction gear and gear housing, an auxiliary transaxle casing secured to the main transaxle casing, a first wheel drive gear unit to split driving power from the final reduction gear into two components and including a differential gear assembly enclosed in the auxiliary transaxle casing and operative to transmit one of the power components to a pair of road wheels, a second wheel drive gear unit enclosed in the auxiliary transaxl