Abstract: There is disclosed a drive force transmission apparatus which includes a first pressing-force generation unit for generating a pressing force in accordance with a rotational speed difference between driving and driven shafts, and a frictional clutch which is brought into an engaged state by the pressing force generated by the first pressing-force generation unit in order to transmit torque in accordance with the rotational speed difference between the driving and driven shafts. The drive force transmission apparatus further includes a second pressing-force generation unit disposed opposite to the first pressing-force generation unit with respect to the frictional clutch. When needed, the second pressing-force generation, unit is operated to bring the frictional clutch into a firmly engaged state, thereby improving the traveling performance of the vehicle under severe traveling conditions, such as an attempt to extract a wheel trapped in a gutter or the like, traveling on a rough road, traveling on sand, etc.

Abstract: A drive force transmission apparatus includes a housing connected to one of two shafts that are rotatable relative to each other, a rotary shaft rotatably supported by the housing and connected to the other shaft, and a multiple disc clutch composed of a plurality of outer plates engaged with the housing in the rotational direction and a plurality of inner plates engaged with the rotary shaft in the rotational direction. The multiple disc clutch transmits rotational torque between the housing and the rotary shaft through frictional engagement between the outer plates and the inner plates. The apparatus also includes a pressure generation mechanism for generating a pressure corresponding to a rotational-speed difference between the housing and the rotary shaft and for applying the generated force to the multiple disc clutch via a piston.

Abstract: A gear-shift mechanism for a transmission unit which includes a fork shaft slidably supported in a housing assembly which is selectively shifted from its neutral position to forward and reverse positions, a detent mechanism for selectively retaining the fork shaft in its neutral and shifted positions, a shift head member slidable on the fork shaft, a one-way engagement mechanism for effecting the engagement between the shift head member and the fork shaft during axial displacement of the fork shaft toward and away from its reverse position, and a shift arm member pivotably mounted to the inner wall structure of the housing assembly and linked with the shift head member to retain an idler gear in its neutral position and engage the same with driving and driven gears. The detent mechanism includes a first holder member having a slot in its upper portion and a shaft fixed to the upper side portion of the first holder member and a second holder member fitted into the first holder member.

Abstract: A gear-shift mechanism for a manual transmission includes first, second and third shift heads arranged in sequence, the first and second shift heads each being operatively connected to first and second synchronizers respectively for establishing first and second speed gear trains and for establishing third and fourth speed gear trains, and the third shift head being operatively connected to a shift fork for establishing a reverse gear train, and further includes a shift-and-select lever operatively connected to a manual shift lever to be axially shifted in selecting operation for selective engagement with the shift heads and to be rotated at its shifted position in shifting operation for establishment of the selected gear train.

Abstract: A transmission unit comprises a differential gear unit having a pair of side-journals rotatably supported by a pair of axially spaced side-bearings carried on a pair of carrier portions of a casing for the transmission unit, a pair of wheel axles extending outwardly through the respective side-journals from the differential gear unit in an opposite direction and surrounded by a pair of annular seal members carried on the respective carrier portions, a pair of annular shim plates interposed between each of the carrier portions and each of the side-bearings, and a pair of oil passages for leading lubricating oil into a pair of annular side-spaces formed around each of the wheel axles between the respective side-bearings and the respective seal members.