GASKET 5L8787 - Caterpillar

Illustration 14 g00530337
Partially Depressed Center PedalPlunger at TopSystem components (2) Operate/brake valve spool (4) Brake line (5) Charge pressure check valve (7) Start/vent spool (8) Speed/brake control spool (48) Orifice (A) FORWARD (B) Brakes OFF (C) PARK (D) Brakes OFF (E) REVERSE (M) Passage to underspeed valve (N) Pu oil (P) Oil from valve spool (Q) Passage to the drain (AA) Supply oil from the charge pump (BB) Supply oil for servo valves (EE) Charge oil to the drive loops (HH) Blocked oil (LL) Return oil and charge pump supplyWhen the operator partially depresses the center pedal, the position of the components indicates pedal movement. The pedal moves until the pedal just makes contact with the top of the spring loaded plunger.The plunger is installed in the base of the pedal. The plunger serves as a stop. When the operator depresses the pedal to this position (plunger at top), the underspeed valve moves to FULL DOWN.A spacer is installed at the bottom of the underspeed valve. The spacer controls the position of the underspeed roller when the underspeed valve is fully down. If the transmission control lever is in a FULL directional position, the spacer does not allow the underspeed valve to move down far enough. (Place the control lever in FULL FORWARD or FULL REVERSE.) The mechanical linkage moves the servo valves to a centered position or PARK position.As a result, a small amount of machine movement still occurs. When the servo valves are near PARK position, the swashplates are near ZERO angle. This reduces the flow through the drive loops. Then, the machine slows. (This is called dynamic braking.)The chamber at the left end of operate/brake valve spool (2) is connected through an internal passage in the valve body to a second passage in the speed/brake control spool.When the center pedal is NOT depressed, the oil in the chamber at the left end of the operate/brake valve spool does NOT connect to the drain passage in the valve body. When the center pedal is partially depressed, the same condition occurs.Due to the position of the speed/brake spool, the operate/brake valve spool remains shifted. This continues to provide oil to the brakes. If the operate/brake valve spool moved left, the flow to the brakes would stop. The brakes would engage.
Illustration 15 g00530642
Fully Depressed Center PedalFully Depressed PlungerSystem components (2) Operate/brake valve spool (4) Brake line (5) Charge pressure check valve (7) Start/vent spool (8) speed/brake control spool (48) Orifice (A) FORWARD (B) Brakes OFF (C) PARK (D) Brakes OFF (E) REVERSE (M) Underspeed valve (N) Pu oil (P) Oil from valve spool (Q) Passage to the drain (AA) supply oil from charge pump (BB) Supply oil for servo valves (EE) Charge oil to the drive loops (HH) Blocked oil (LL) Return oil and charge pump suctionAfter the center