Figure 2-6.—Automatic transmission cross-sectional view.

2-8speeds and some are equipped with overdrive. Operator control is limited to the selection of the gear range by moving a control lever. Part of the prestart operation is to check the transmission fluid level when the engine is idling and at normal operating temperature, when the vehicle is level, and when the transmission control lever is in park. The transmission fluid is used as a combination power transmission medium, hydraulic control fluid, heat transfer medium, bearing surface lubricant, and gear lubricant. The manufacturer’s recomendations must be followed when servicing and filling the transmission with fluid. CAUTION Do not overfill the transmission because overfilling causes foaming and shifting troubles. Some transmission troubles you may encounter and must document are as follows: . No drive in any selected positions. On standstill starts the engine speed accelerates but the vehicle movement lags. Engine speed accelerates during upshifts. Transmission will not upshift. Upshift and downshift are harsh. Vehicle creeps too much in drive. Vehicle creeps in neutral. Improper shift points. Unusual transmission noise. Oil leaks. Fluid Couplings In the past, fluid couplings were widely used with automatic transmissions. Fluid couplings act like an automatic clutch by slipping at idling speeds and by holding to increase power as the engine speed increases. There is no mechanical connection between the engine and transmission; power is transmitted by oil. Figure 2-6.—Automatic transmission cross-sectional view. 2-5