BUCKET AS-HEAVY DUTY 3476741 - Caterpillar

Illustration 1 g01077668
Scraper Transmission Hydraulic Controls In "FIRST" (1) Magnetic screen (2) Transmission charging section (3) Transmission oil filter (4) Synchronizing solenoid (5) Lockup clutch valve (6) Lockup clutch and synchronizing valve (7) Retarder hydraulic control valve (8) Transmission oil cooler (9) Retarder air valve (10) Retarder (11) Scavenge section of transmission oil pump (12) Screen (13) Transmission oil tank (14) Reservoir in transmission case (15) Synchronizing valve (16) Orifice torque converter outlet pressure (17) Torque converter (18) Transmission lubrication relief valve (19) Upshift solenoid (20) Downshift solenoid (21) Selector valve (22) Priority valve (23) Priority valve body (24) Selection spools (25) Shift cylinder valve spool (26) Shift cylinder body (27) Pressure control valve (28) Torque converter inlet valve (29) Combination valve spool (pressure differential, safety, check and flow control) (30) Load piston (31) Modulation relief valve (A) Pressure tap for the lockup clutch (B) Pressure tap for transmission oil pump at the oil filter (C) Pressure tap for converter outlet (D) Pressure tap for transmission oil pump at the lockup clutch and synchronizing valve (E) Pressure tap for transmission lubrication (F) Pressure tap for speed clutch (P1) (G) Pressure tap for direction clutch (P2) (H) Pressure tap for torque converter inlet (P3) (I) High pressure oil (J) Return oil (K) Lubrication oil (L) First reduction pressure oil (M) Second reduction pressure oil (N) Tank oilProtective Operation
When the scraper engine is stopped, combination valve spool (29) moves all the way to the left against the valve body of pressure control valve (27) .If the scraper is started with the selection lever in any position except NEUTRAL, the oil from transmission charging section (2) flows through selector valve (21) to a chamber in the center of combination valve spool (29). At the same time, oil also flows to the left end of combination valve spool (29). The pressure at the left end of combination valve spool (29) is equal to the pressure of the oil in the chamber. The pressure of the oil in the chamber adds with the force of the spring. The force of the spring and the pressure of the oil in the chamber keeps combination valve spool (29) all the way to the left against the valve body of pressure control valve (27). The combination valve spool (29) is kept in this position. Oil does not flow to the direction clutches. A direction clutch does not engage. Since both a direction clutch and a speed clutch must be engaged before power flows through the scraper transmission, the scraper does not move.Neutral Operation
Transmission charging section (2) pumps oil to the transmission oil filter (3). Oil from filter (3) flows to the following four locations:
The lockup clutch and synchronizing valve
Priority valve (23)
Shift cylinder (26)
Pressure control valve (27) The