Usage:
771D (6YS),
775D (8AS) Quarry Trucks;
769D (5SS),
773D (7CS) Off-Highway Trucks
Description of Change: There are illustrations and operation descriptions in both manuals listed below that are incorrect. The corrections, which apply to BOTH manuals, will be listed following the manual titles.
Service Manual Module, SENR1555; December 1998, 769D Off-Highway Truck & 771D Quarry Truck Air System and Brakes; Systems Operation Testing and Adjusting Manual; This module is found in Service Manual SENR1545, 769D Truck & 771D Quarry Truck, Volume II.
Service Manual Module, SENR1578; December 1998, 773D Off-Highway Truck & 775D Quarry Truck Air System and Brakes; Systems Operation Testing and Adjusting Manual; This module is found in Service Manual SENR1565, 773D Truck & 775D Quarry Truck, Volume II.
NOTE: As of June, 1999, all corrections have been made and are available in Service Manual Module SENR1555, SENR1578, and the Service Information System (SIS).
On Page 4, Air System Schematic, Illustration 1 is incorrect. Disregard Illustration 1 and use the following illustration.
Illustration 1.
On Page 22, the last paragraph in the right column is incorrect and should read as follows:
The parking brake air control valve is located in the control console near the transmission control. The parking brake air control valve controls air flow to the parking and secondary brake valve.
On Page 23, the last paragraph in the left column is incorrect and should read as follows:
Air flows out of delivery passage (5) to the parking secondary brake valve. The air flow pushes down a spool in the parking and secondary brake valve. This allows oil flow to release the spring applied parking brakes for the rear wheels.
On Page 23, the first paragraph in the right column is incorrect and should read as follows:
When lever (2) is moved to the ON position, lever (2) releases plunger (1). Spring (6) raises plunger (1) off inlet valve (7). Spring (9) pushes inlet valve (7) against valve seat (8). The air flow from supply passage (10) is blocked. Delivery passage (5) remains open. The air from the parking and secondary brake valve flows through passage (3) in plunger (1). This air exits the parking brake air control valve through exhaust passage (4).
On Page 23, the last paragraph in the right column is incorrect and should be disregarded.
On Page 28, the explanation of the operation of the "Inverter Valve (Front Brake)" is incorrect and should read as follows:
The front brake inverter valve is located above the primary air tanks on the right hand platform next to the cab. When the secondary brake control is applied, the front brake inverter valve allows air to flow to the front brake master cylinder in order to apply the hydraulic caliper service brakes.
Air supply from the secondary air tank flows into supply port (2) of the front brake inverter valve. Air pressure from the secondary brake inverter valve flows into signal port (1). When the pedal for the secondary brake air control valve is fully applied, air pressure to signal port (1) is blocked. This causes the front brake inverter valve to open the passage from supply port (2) to output port (4). Air pressure now flows through a double check valve to the front brake master cylinder. The front brake master cylinder sends oil pressure in order to apply the hydraulic caliper service brakes for the front wheels.
When the secondary brake control is partially depressed, the front brake inverter valve partially allows the air pressure to flow to the front brake master cylinder. The hydraulic caliper service brakes will be partially applied. When the secondary brake control is released, full air pressure flows to signal port (1). Outlet port (4) will be blocked and air will be open to exhaust port (3). The outlet pressure is discharged through exhaust port (3).
On Page 29, the second paragraph in the right column is incorrect and should read as follows:
Front brake inverter valve (6) is used to engage the front brakes when the secondary brake pedal is pressed. Front brake inverter valve (6) will engage the front brakes even if the front brake control is in the OFF position.
On Page 30, the first paragraph in the right column is incorrect and should read as follows:
When the service brake pedal is applied, the front brake air relay valve delivers air to air chamber (1). When the secondary brake pedal is applied, front brake inverter valve delivers air to air chamber (1). The pressurized air pushes piston (2) and rod (3). This compresses spring (4). Rod (3) moves valve (6) in order to close passage (7). As power piston (8) moves down, oil in the brake master cylinder flows out of port (10) to the slack adjuster. The oil moves the pistons in the hydraulic caliper service brakes.
On Page 32, Illustration 54 is incorrect. Disregard Illustration 54 and use the following illustration.
Illustration 54.
On Page 33, the last paragraph in the left column is incorrect and should be disregarded.
On Page 34, Illustration 55 is incorrect. Disregard Illustration 55 and use the following illustration.
Illustration 55.
On Page 36, Illustration 56 is incorrect. Disregard Illustration 56 and use the following illustration.
Illustration 56.
On Page 38, Illustration 57 is incorrect. Disregard Illustration 57 and use the following illustration.
Illustration 57.
On Page 40, Illustration 58 is incorrect. Disregard Illustration 58 and use the following illustration.
Illustration 58.
Adaptable To: 771D (6YS1-Up), 775D (8AS1-Up), 769D (5SS1-Up), 773D (7CS1-Up)