Planetary Gear SystemA torque converter alone cannot supply the torque multiplication needed for all driving conditions. The torque converter therefore drives through a planetary gear system which can operate at different drive ratios. The planetary gear system consists of two clutches, two brakes, and two planetary gear-sets-one gearset for forward operation of the vehicle and the other gearset for reverse. The two hydraulically-operated multiple-disc clutches control the routing of power to the planetary gearsets. The clutch at the right-hand end of the transmission is called the forward clutch because it transfers power to the planetary gears in all forward gears. The clutch at the left-hand end of the transmission is called the direct and reverse clutch because it transfers power to the planetary gears only when the transmission is in direct drive (3rd or top gear) or reverse. The first of the two brakes is the 2nd-gear brake band. It contracts around the direct and reverse clutch drum to provide 2nd gear. The second of the two brakes is the 1st/reverse gear brake. It is applied hydraulically to obtain reverse. This brake is also applied when the selector lever is at 1 in order to provide additional engine braking by locking the normally freewheeling 1st gear one-way clutch. |
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