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 shift control mechanism is provided for a multiple-forward-speed manual transmission which controls operation of the shift lever between the reverse drive position and one forward drive position to prevent inadvertent shifting which might damage the transmission. A transmission lever whose movement is controlled through the shift lever is formed with a projection extending therefrom which is adapted to engage a movable pin mounted in a housing. The housing is axially movable along a guide shaft and the pin is movable between an extended and a retracted position relative to the housing. The erroneous shifting operation between the reverse drive position and the one forward drive position is prevented by engagement between the projection and the pin in a manner which does not interfere with appropriate shifting of the transmission during vehicle operation.

Abstract: A shift control mechanism is provided for a multipleforward-speed manual transmission with controlled operation of the shift lever between the reverse drive position and one forward drive position to prevent inadvertent shifting which might damage the transmission. A transmission lever whose movement is controlled through the shift lever is formed with a first projection extending therefrom which is adapted to engage a second projection extending from a housing. The housing is rotatably and linearly movable under the biasing force of spring means and when the shift lever is moved to the neutral position, engagement between the first and second projections will cause rotative movement of the housing. When the shift lever is moved to the one forward drive position, the spring means will rotate the housing back to its initial position thereby placing the second projection within the path of movement of the first projection.