RAM 1500 Van V8-5.9L VIN Z LDC (2001)
The PCM energizes the overdrive solenoid during the 3-4 upshift (Fig. 274). This causes the solenoid check ball to close the vent port allowing line
pressure from the 2-3 shift valve to act directly on the 3-4 upshift valve. Line pressure on the 3-4 shift valve overcomes valve spring pressure moving
the valve to the upshift position (Fig. 275). This action exposes the feed passages to the 3-4 timing valve, 3-4 quick fill valve, 3-4 accumulator, and
ultimately to the overdrive piston.
3-4 TIMING VALVE
The 3-4 timing valve is moved by line pressure coming through the 3-4 shift valve (Fig. 276). After the shift, the timing valve holds the 2-3 shift valve
in an upshift position. The purpose is to prevent the 2-3 valve from downshifting before the 3-4 valve (Fig. 274).
3-4 QUICK FILL VALVE
The 3-4 quick fill valve provides faster engagement of the overdrive clutch during 3-4 upshifts. The valve temporarily bypasses the clutch piston feed
orifice at the start of a 3-4 upshift (Fig. 274). This exposes a larger passage into the piston retainer resulting in a much faster clutch fill and apply
sequence. The quick fill valve does not bypass the regular clutch feed orifice throughout the 3-4 upshift. Instead, once a predetermined pressure
develops within the clutch, the valve closes the bypass (Fig. 275). Clutch fill is then completed through the regular feed orifice.
THROTTLE VALVE