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Valvebody Basics. Transmission Hydraulic Pressures. Mainline Pressure Throttle Pressure Governor Pressure. Pressure Regulation. Regulator Valve Variable Regulated Pressure . Building to Max Pressure. Pressure Regulator Valve. Bleeds off pressure when maximum pressure is reached.
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Transmission Hydraulic Pressures Mainline Pressure Throttle Pressure Governor Pressure
Pressure Regulation • Regulator Valve • Variable Regulated Pressure Building to Max Pressure
Pressure Regulator Valve • Bleeds off pressure when maximum pressure is reached. • Exhausts back to sump • If left unregulated can damage components
Mainline Pressure(“line pressure”) • Regulated Mainline Pressure is source for all flow • Controlled by pressure regulator • Applies bands and clutches • Feeds Valve Body valves • Applies pressure to one end of pressure regulator valve
BOOST PRESSURE • Boosted Mainline Pressure • Boost Valve to raise pressure at low rpm and high engine load • Other pressures are used to modify regulated pressure
Throttle Pressure(“modulated pressure”) • Engine Load Sensing • Mechanical • Vacuum • Works against governor pressure • Primary Shift Control signal • Always less or equal to mainline pressure
Road Speed signal Opposes TV pressure to control shift points Driven by output shaft Higher speeds = Higher pressure Governor Types Gear Driven Spool Valve Type Check-ball Type Shaft Mounted Valves allow fluid to not bleed off the higher speed you go. Governors stick sometimes and can be cleaned Governor Pressure
Centrifugal Governor Operation Spool Valve operated
Shifting and Shift Operations • Manual Valve • Throttle Valve • Downshift Valves • Governor Valve • Spool Valve design • Check-ball design • Shaft Mounted governors
Manual Valve Operation • Positioned manually by gear selector lever • Lever moves valve to one of several detent positions • Directs mainline pressure to correct shift valves and apply devices
Shift Valve Operation • Shift Valves are: • Flow directing • Switching valves • Spool Type valves • Governor Pressure on one end • Throttle Pressure on other end with spring assist • Blocks or allows fluid flow • Valves must move instantly
Shift Valve Operation -When speed is high, governor pressure is higher than throttle pressure. -Allows mainline pressure to pass through and cause a upshift When Vehicle speed low Throttle pressure and spring Pressure are higher than Governor pressure
Hydraulic CircuitLow Gear • 1 – 2 Shift valve controls upshifts and downshifts between • first and second gears • 2 –3 shift valve controls upshifts and downshifts between second and third gears