TM10-3930-660-34 CHAPTER 7 TRANSMISSION NAINTENANCE Section I.  DESCRIPTION AND DATA 7-1. GENERAL. This chapter covers maintenance procedures for the transmission, as well as principles of operation. 7-2. PRINCIPLES OF OPERATION. a. General.  The transmission has four forward and four reverse speeds, with speed and direction controlled by hydraulic operated clutches. Engine torque is coupled to the transmission through the torque converter (1). b. Torque Converter.  The torque converter (1) couples engine torque to the transmission input shaft. It is basically a fluid drive, which has no mechanical connection through it. This feature not only eliminates nearly all wear, but also provides a smooth and almost shock-free drive which prevents engine stalling and lugging. Under light loads, engine speed is transmitted at almost a 1:1 ratio through the torque converter. As loads increase, however, the torque converter inherently multiplies engine torque. The need to manually shift transmission gears is therefore greatly reduced, but not totally eliminated. c. Clutches.  The clutches are hydraulically applied and spring released. Using hydraulic power to control clutch application permits automatic compensation for clutch wear; therefore, there is no need for clutch adjustment. Each clutch contains a number of paper graphitic friction plates and polished steel reaction plates. Clutch actuation determines speed and direction of rotation of output shafts (2 and 3), which transmit power to the respective axle differentials. 7-1