Part Throttle 4-3 & Modulated Downshifts (Valves In 3rd Gear)

With 4L60 (700-R4) Transmissions - 4WD Shown, 2WD Similar:

PART THROTTLE 4-3 AND MODULATED DOWNSHIFTS (Valves In Third Gear Position)

CONVERTER CLUTCH - APPLIED*
FORWARD CLUTCH - APPLIED
FORWARD SPRAG CLUTCH - HOLDING
3-4 CLUTCH - APPLIED

A part throttle 4-3 downshift can be accomplished by depressing the accelerator pedal far enough to move the throttle valve (T.V.) plunger to allow the T.V. oil to enter the part throttle (P.T.) passage. This oil, called part throttle (P.T.) oil, is then routed to the 3-4 throttle valve.

Part throttle oil and the 3-4 throttle valve spring force will close the 3-4 shift valve against governor pressure, shutting off D4 oil to the fourth signal passage. Fourth accumulator oil will push the 3-4 relay valve closed and hold the 4-3 sequence valve open while it exhausts at an orifice at the T.V. limit valve. Fourth oil will pass through the 4-3 sequence valve to the servo feed passage to the 2-3 shift valve to the fourth accumulator passage. When fourth accumulator pressure is low enough, the 4-3 sequence valve spring will close the 4-3 sequence valve and the remaining fourth and fourth accumulator oil will exhaust at the 4-3 sequence valve.

A type of part throttle downshift can be accomplished in some ranges (4-3, and 3-2, shifts) by depressing the accelerator pedal far enough to raise Modulated Throttle Valve (M.T.V.) down pressure. This pressure when combined with the throttle valve spring pressure can overcome governor pressure and cause a modulated downshift.

*The converter clutch will be released for the 4-3 downshift and may or may not be reapplied depending on shift calibration and solenoid operation.