Abstract: Described herein is a hydraulic servo for a friction coupling element of an automatic transmission, which is mounted in association with a one-way clutch and which has reduced dimensions in radial and axial directions. The hydraulic servo essentially comprises: an annular drum splined with a sleeve portion of the inner race of the one-way clutch and arranged to receive the reaction of the one-way clutch by a fixed member in the automatic transmission case; a piston fitted in the annular drum; and a return spring mounted in the drum for returning the piston.

Abstract: Provided is a power transmission device for four-wheel drive vehicles of both the full-time type and part-time types, wherein a wet multiple-disc clutch is mounted in a ring gear covering the front-wheel differential gear and arranged coaxially with the differential gear. The wet multiple-disc type clutch is engaged by means of a hydraulic actuator in which a plurality of pistons are arranged in series. Hydraulic pressure is fed into oil chambers formed by the pistons through individual or common oil passages. The wet multiple-clutch constitutes a differential motion limiting device for stopping or limiting the differential motion of a center differential gear for the full-time four wheel drive, or constitutes a rear wheel drive switching unit for engaging and disengaging the power transmission between the ring gear mount casing and the transfer unit.

Abstract: A supporting mechanism for a transmission shaft in an automatic transmission apparatus for use in a vehicle, wherein said shaft is rotatably supported at both end portions (1A), (1C) and at the intermediate portion (1B), and the amount of play of said shaft at said intermediate portion is set greater than those at the end portions, with a view to preventing oscillation of the shaft at the intermediate portion between the supporting points and favorably overcoming difficulty in assembly work, e.g., centering associated with supporting at three points.

Abstract: A power transmission device for a full-time four wheel drive vehicle has a differential motion limiting device composed of a hydraulic frictional clutch such as a wet multiple disc type clutch. The friction clutch is disposed between a diff-carrier constituting a front wheel differential gear and a ring gear mount casing covering the diff-carrier and arranged coaxially with the diff-carrier. The ring gear mount casing is associated with the diff-carrier in a center differential gear, and the diff-carrier of the front wheel differential gear is associated with the left hand side gear in the center differential gear. Thus, when the friction clutch is engaged, the ring gear mount casing and the diff-carrier of the front wheel differential gear are integrally coupled with each other so that the rotation of the ring gear is transmitted directly to the front wheel differential gear, while the two elements in the center differential gear are integrally coupled with each other to lock the center differential gear.

Abstract: A center differential gear adapted for use in a power transmission device for full-time type four-wheel drive vehicles includes a diff-carrier coupled with a power transmitting front casing covering the front diff-carrier of a front-wheel differential gear and arranged coaxially with the diff-carrier, a side gear coupled to the front wheels, and another side gear coupled to a gear mount casing which transmits power to the rear wheels. The diff-carrier of the center differential gear is supported between the side gear on the side driving the front-wheel differential gear and the gear mount casing in cantilever fasion. The other side gear is spline-coupled directly to the gear mount casing without passing through the diff-carrier.

Abstract: Described herein is a hydraulic servo drum which is compact in construction and defines an appropriate area for a piston, the servo drum including: an annular plate member having a press-formed cylindrical portion around the outer periphery thereof; an intermediate cylinder member having one end thereof fitted on the cylindrical portion of the annular plate member and formed with a spline in the remaining portions; and an outer cylinder member provided with a folded portion at one end thereof and having the inner periphery of the folded portion connected to the intermediate cylinder member.

Abstract: Described herein is a hydraulic servo suitable for friction coupling elements in automatic transmissions. The hydraulic servo of the invention is compact in construction and reduced particularly in axial dimensions, and essentially comprises: an annular drum rotatably or fixedly mounted in a transmission case and having a press-formed annular plate member with an first cylinder portion and a second cylinder member joined to the first cylinder portion by fully encircling welding; a piston fitted between the first cylinder portion and the second cylinder member; and a reaction area formed by extending the annular plate member of the drum radially inward to support return springs.