1. Field of the Invention
The invention relates to a transmission for a motor vehicle, and more particularly to a transmission comprising an input shaft, a countershaft, and an output shaft arranged concentrically with the input shaft and the output shaft journalled to the input shaft, a pair of gearwheels arranged between the input or output shaft, and the countershaft constituting a constant ratio, and a plurality of pairs of gearwheels carried on the gear shafts and each comprising a fixed gearwheel and a loose gearwheel for engaging the various gear steps.
2. Description of the Prior Art
A prior art transmission is shown in German specification 34 45 519 (DE '519). As shown in FIG. 1 of the DE '519 patent, the input shaft and output shaft and/or the countershaft are mounted in three bearings and a synchronizer unit for engaging the 5th gear and the reverse gear is provided on the countershaft.
The transmission in the DE '519 patent has the disadvantage that the gearwheel pair for the constant ratio is arranged directly on a short input shaft and at the input end of the countershaft for all the following gear steps. This results in the disadvantage that when the transmission is in the neutral position with the friction clutch engaged, the input shaft constantly drives the countershaft. Thus, by way of the fixed gearwheels carried on the countershaft, the corresponding loose gearwheels on the output shaft are also driven. This leads to undesirable rattling noises in neutral, which arise from the various imperfections in the gear teeth and play between the teeth.
German specification 37 29 818 (DE '818) discloses a similar transmission, wherein a synchronizer unit for engaging the 5th gear and the synchronized reverse gear is carried on the output shaft.
The transmission of the DE '818 patent again has the disadvantage that the constant ratio is arranged directly between a short input shaft and the input end of the countershaft, and accordingly in the neutral position of the transmission with the friction clutch engaged the whole set of gearwheels on the countershaft rotates, whereby, owing to the loose gearwheels being in mesh with the fixed gearwheels, and therefore marked rattling noises can be caused.
It would therefore be desirable to provide a transmission having a neutral position wherein the gear ratios are not driven and therefore less gear noise occurs. A further object is to provide six forward gears and a synchronized reverse in such a transmission.