Drive Range-1ST Gear

In this range, the converter clutch is released, the overdrive roller clutch is holding, the forward clutch is applied, the lo roller clutch is holding and the transmission is in Drive (D) range first gear.

With the selector lever in the Drive (D) position, the manual valve is positioned to permit line pressure to enter the Drive 4 (D4) passage. Drive 4 oil then flows to the forward clutch, where it acts on the clutch piston to apply the forward clutch; to the 1-2 shift valve, where it seats the 1-2 check ball and is directed through an orifice before acting on the 1-2 shift valve; and to the accumulator valve, where its pressure is regulated (accumulator pressure) and directed to the 1-2 and 3-4 accumulator pistons to cushion the band and fourth clutch apply.

Drive 4 oil is also orificed into the governor passage and is regulated to a variable pressure (governor pressure). Governor pressure increases with vehicle speed and acts against the 1-2,2-3,3-4 and converter clutch shift valves and the 3-2 control valve.

In first gear, there may be sufficient throttle valve plunger travel to increase T.V. pressure enough to open the T.V. modulator upshift valve (M.T.V. up) and the T.V. modulator downshift valve (M.T.V. down). The T.V. modulator upshift valve delays upshifts, when conditions such as heavy acceleration exist, by assisting the shift valve springs in holding the shift valves closed. The T.V. modulator downshift valve enables downshifts to occur at higher vehicle speeds by assisting the shift valve springs in closing the shift valves.