Before First 1-2 Shift

Overdrive Range, First Gear (Before First 1-2 Shift)





When the gear selector lever is moved to the Overdrive range position (D), from the Neutral (N) position, before the first 1-2 shift has occurred, the following changes occur to shift the transmission into Overdrive Range - First Gear.
Manual Valve: In the Overdrive position the manual valve routes line pressure into the D432 fluid circuit. D432 fluid is routed to the 1-2 shift valve and to the 3-4 shift valve.

Forward Clutch Applies
#6 and #7 Ball Check Valves: D432 fluid seats the #6 ball check valve and passes through orifice #15 into the forward clutch fluid circuit. D432 fluid also passes by the spring loaded #7 ball check valve to feed the forward clutch circuit as necessary to help control forward clutch apply.
Forward Clutch Assembly: Forward clutch fluid is routed to the forward clutch piston to apply the forward clutch plates.

Coast Clutch Applies
#5 Ball Check Valve: Forward clutch fluid seats the #5 ball check valve and passes through orifice #17 into the coast clutch feed circuit. This orifice helps to control coast clutch apply.
Safety Mode Valve: Before the first 1-2 shift has occurred, the safety mode valve (34) 1 remains in the released position, allowing line fluid pressure to enter the line safety mode fluid circuit.
4-5 Shift Valve: Line safety mode fluid applies the 4-5 shift valve (374) against 4-5 shift valve spring (373) force. This allows coast clutch feed fluid to enter the coast clutch fluid circuit.
Coast Clutch Assembly: Coast clutch fluid is routed to the coast clutch piston to apply the coast clutch plates.

Low and Reverse Clutch Applies
2-3 Shift Solenoid (SS) Valve: The 2-3 SS valve is energized. allowing feed limit fluid to enter the 2-3 signal fluid circuit 2-3 signal fluid overcomes spring force and applies the 2-3 shift valve (371).
3-4 Shift Control Valve and 3-4 Shift Valve: 2-3 signal fluid is routed to the 3-4 shift control valve (346) arid applies the valve against spring force. This allows D432 fluid to enter the 123 fluid circuit.
#4 Ball Check Valve: 128 fluid seats the #4 ball check valve and passes through orifice #16. This orifice helps to control low and reverse clutch apply.
4-5 Shift Valve: Orificed 123 fluid is routed to the 4-5 shift valve (374) where it passes into the 123 braking fluid circuit.
Low Pressure Control Valve: 123 braking fluid is routed to the low pressure control valve (383). This valve regulates 123 braking fluid into the 123 regulated fluid circuit against spring force and orificed 123 regulated fluid pressure.
1-2 Shift Control Valve and 1-2 Shift Valve: 2-3 signal fluid is also routed to the 1-2 shift control valve (366) and applies the valve against spring force. This allows feed limit fluid to enter the FDL fluid circuit. FDL fluid is routed to the 1-2 shift valve (387) and applies the valve against spring force 123 regulated fluid is routed through orifice #20 to the 1-2 shift valve where it passes into the low and reverse clutch fluid circuit.
#8 Ball Check Valve: Low and reverse clutch fluid seats the #8 ball check valve against the reverse lockout fluid passage and enters the low and reverse clutch or reverse lockout fluid passage.
Low and Reverse Clutch: Low and reverse clutch or reverse lockout fluid pressure enters the outer area of the low and reverse clutch piston and moves the piston against spring force to apply the low and reverse clutch plates.

Fluid Pressure Directed in Preparation for a Shift to Second Gear
1-2 Shift Valve: D432 fluid is routed to the 1-2 shift valve (387) where it is blocked by the valve in preparation for an upshift to second gear.