Multiple-speed gearbox of 3-shaft design, especially for motor vehicles

A multiple-speed gearbox for motor vehicles, comprising:

• a first input shaft;
• a second hollow input shaft concentric with and surrounding the first input shaft;
• first and second mutually parallel countershafts substantially parallel to the input shafts, the first countershaft having an output drive pinion driveably connectable to an output shaft;
• first and second selectively switchable friction clutches, the first clutch connected to the first input shaft, the second clutch connected to the second input shaft;
• pairs of meshing gears, each pair having a first member supported on one of the first and second input shafts and a second member supported on one of the first and second countershafts, each pair having a gear fixed to the shaft on which it is supported and a gear journalled on the shaft on which it is supported;
• synchronizers for driveably connecting the journalled gears to the shafts on which they are supported located, a first synchronizer located between two journalled gears supported on the first input shaft, a second synchronizer located between two journalled gears supported on the second input shaft, a third synchronizer located between two journalled gears supported on the first countershaft, a fourth synchronizer located between two journalled gears supported on the first countershaft;
• and
• the first input shaft connectable to the second input shaft by a synchronizer clutch.