The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
A typical manual transmission includes a plurality of shafts, gears, shift mechanisms, synchronizers or other torque-transmitting mechanisms that cooperate to provide a plurality of forward and reverse gear or speed ratios. The transmission input shaft is selectively connected to an engine output shaft and includes a number of gears that are selectively connectable to the input shaft using, for example, synchronizers. The gears of the input shaft mesh with corresponding gears that are selectively connectable to an output shaft. To achieve a particular forward gear ratio between the transmission input and output shafts, the driver operates a shift mechanism, such as a manual shifter, that controls the engagement of the synchronizers with the desired gears. To achieve a reverse gear ratio, an idler gear is used to slide between an input shaft gear and an output shaft gear to reverse the rotational direction of the output shaft, and thus the drive wheels.
The idler gear is free to rotate on an idler gear shaft and the idler gear is not necessarily rotating when the idler gear is engaged to the input shaft reverse gear. However, the input shaft reverse gear is often rotating at a high speed having only recently been disengaged from the engine output shaft. Once the idler gear is meshing with the input shaft reverse gear they will both be rotating at the same high speed. The idler gear must then engage the output shaft gear to complete the torque transfer to the output shaft. However, as often is the case, the output shaft is not rotating and may even be rotating in the opposite direction as the driver may be shifting into reverse before the vehicle has stopped moving forward. The meshing of the fast rotating idler gear with a stationary output gear causes an impact or gear clash that creates noise and grinding that is very objectionable to the driver. Furthermore, gear clash is detrimental to the long term durability of the transmission and is the source of costly customer repair bills.
Accordingly, there is room in the art for a transmission that includes a mechanism to reduce or eliminate gear clash and premature component wear by reducing the input shaft and idler gear rotational speed when the driver is shifting into a reverse gear ratio.