Gearbox switchable under load

A gearbox switchable under load between a number of different driving speed gear stages comprising:

• an input shaft, said input shaft is rotatively fixedly connected to an engine shaft, at least one further shaft coupled with said input shaft and extending parallel to said input shaft;
• pairs of gearwheels for, achieving different driving speed gear stages coupled with said shafts, one gearwheel of each pair of gearwheels being rotatively fixedly connected to one of the two shafts and the other gearwheel of each pair of gearwheels being optionally rotatively fixedly connectable to the other of the two shafts by a respective friction coupling;
• means for reversing the direction of rotation in the torque flow from the input shaft to an output pinion, said reversing means associated with at least one of said shafts;
• means for approximately simultaneously loading friction couplings of two lowest driving speed gear stages for commencing torque transmission in a forward driving gear and for commencing torque transmission in a reverse gear, torque flow through said friction couplings being maintained, at most, until an identical speed has been reached between the elements of the friction coupling of the most lowest driving speed gear stage.