BRACE 5T3890 - Caterpillar

Shifting from the NEUTRAL position to the First Speed Forward position with a Running Engine
Illustration 3 g00850544
Transmission Hydraulic Controls in the First Speed FORWARD position
(1) Number 2 clutch solenoid
(2) Number 3 clutch solenoid
(5) Number 5 clutch solenoid
(7) Flow control orifice
(10) Slug
(11) Converter inlet ratio valve
(13) Modulating relief valve
(16) Direction selection spool
(19) Selector spool for first speed and for third speed
(21) Pressure differential valve
(22) Load piston
(AA) Speed clutch oil P1
(BB) Direction clutch oil P2
(CC) Converter inlet oil P3
(DD) Converter outlet oil
(EE) Lubrication oil
(FF) Return oil
(GG) Pilot oil
(HH) Torque converter clutch oil When the transmission is moved to the FIRST SPEED FORWARD position, 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 (16). Spool (16) 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 (19). Solenoid (2) is deactivated. Solenoid (2) also directs oil from the top end of speed selection spool (19) to the reservoir. Spool (19) 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 (21) upward until the large orifice at the top end of valve (21) is closed to pump oil by the valve body.As the pressure differential valve (21) moves upward, the chamber behind load piston (22) 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