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

Part Throttle 4-3 And Modulated Downshifts - Valves In Third Gear Position:

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

CONVERTER CLUTCH - APPLIED
OVERDRIVE ROLLER CLUTCH - HOLDING
DIRECT CLUTCH - APPLIED
FORWARD 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 spring force will close the 3-4 shift valve against governor oil, shutting off RND4 oil to the fourth clutch passage. Exhausting fourth clutch and fourth accumulator, oil will pass through the 3-4 shift valve to the 4-3 control valve, which controls the release of the 4th clutch for a smooth 4-3 shift.

A type of part throttle downshift can be accomplished in some ranges (4-3, 3-2, and converter clutch on-off) 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.

Some models will have a different throttle valve bushing, which will block the P.T. passage until the detent passage is opened. These transmissions will have a detent 4-3 or 4-2 downshift. However, a modulated downshift is still possible due to the M.T.V. down valve.