PLATE 8X8916 - Caterpillar

Shifting from the NEUTRAL position to the First Speed Forward position with a Running Engine
Illustration 3 g03879924
Transmission Hydraulic Controls in the First Speed FORWARD position
(1) Priority Valve
(2) Modulating Valve for the Lockup Clutch
(3) Modulating Valve for the Impeller Clutch
(4) Transmission Hydraulic Controls
(5) Power Train Oil Filter for the High Pressure Circuit
(6) Power Train Oil Filter for the Low Pressure Circuit
(7) Torque Converter
(8) Lockup Clutch
(9) Impeller Clutch
(10) Power Train Oil Pump
(12) Oil Cooler
(13) Magnetic Screen
(14) Transmission Lubrication Circuit
(15) Oil Sump in Output Transfer Gear Case
(16) Torque Convertor Outlet Orifice
(17) Rear Pump Drive Lubrication
(18) Front Pump Drive Lubrication
(19) Lubrication Input Transfer
(20) Planetary Lubrication
(21) Output Transfer Lubrication
(22) Differential Valve
(23) Directional Selector
(24) Solenoid 1
(25) Solenoid 2
(26) Ratio Valve
(27) Main Relief Valve
(28) Speed Selector
(29) Solenoid 3
(30) Solenoid 5
(31) Solenoid 4
(32) Load Piston
(33) Speed Selector
(A) Pump Pressure
(B) Speed Clutch Pressure Tap P1
(C) Direction Clutch Pressure P2
(D) Torque Converter Outlet Pressure Tap P3
(E) Pressure Tap for Lockup Clutch
(F) Pressure Tap for Impeller Clutch
(G) Torque Convertor Outlet Pressure Tap
(H) Transmission Lube Pressure Tap When the STIC transmission direction control switch is moved to the FORWARD position and the STIC transmission speed control switch is shifted to FIRST SPEED, solenoids (1) and (5) are activated and solenoid (2) is deactivated. Solenoid (1) moves a spool. Solenoid (1) also directs oil to the top end of direction spool (14). Spool (14) moves downward and pump oil flows around the spool. The pump oil then flows to the Number 2 clutch.Solenoid (5) moves a spool. Solenoid (5) also directs oil to the bottom of speed selection spool (18). Solenoid (2) is deactivated. Solenoid (2) also directs oil from the top end of speed selection spool (18) to the reservoir. Spool (18) moves upward and pump oil flows around the spool to the Number 5 clutch.When the shift to first speed forward is made, the Number 3 clutch is opened to the reservoir. The pressure in the system decreases. Springs move modulating relief valve (13) upward. Springs also move pressure differential valve (19) upward until the large orifice at the top end of valve (19) is closed to pump oil by the valve body.As the pressure differential valve (19) moves upward, the chamber behind load piston (20) opens to the reservoir. This allows the springs to move the load piston downward. The speed clutch oil starts to fill the Number 5 clutch.When the Number 5 clutch is full of oil, the pressure in the speed clutch circuit starts to increase. The increase is felt in the slug chamber of modulating relief valve (13) and in the chamber at the top of pressure differential valve (19).The oil to pressure differential valve (19) starts to fill the chamber at the top of the valve spool through the small orifice.When the pressure in the Number "5" clutch is approximately 380 kPa (55 psi) pressure differential valve (19) starts to move down. The movement of the valve spool opens the Number 2 clutch to pump oil. The movement of the valve spool also closes a