PISTON 1796923 - Caterpillar

The 769C, 773B, and 777 Trucks each have oil cooled multiple disc brakes on the rear, and dry shoe type brakes on the front. Use the front wheel brake valve to either use, or eliminate the use of the front wheel brakes. Four separate controls are utilized for the braking system. The emergency brake control will apply all four wheel brakes, regardless of the front wheel brake valve position. The retarder control will apply only the rear wheel brakes, regardless of the front wheel brake valve position. The parking brake valve will apply only the rear wheel brakes, regardless of the front wheel brake valve position.Each rear wheel disc brake has two pistons to combine all four braking functions into the service brakes. These are the service/retarder piston and the emergency/parking piston. Either the emergency lever or the parking brake valve will release the transmission oil pressure. Then, the compressed springs push the emergency/parking piston against the service/retarding piston to apply the brakes.
If air pressure in the service/retarding tank falls to approx. 60 P.S.I., a low air pressure warning buzzer sounds in the cab. Be prepared to use the emergency system to stop.
If the service brake pedal is used for braking, or retarding, the front wheel brake valve should be off.
Repetitive or continuous use of the front wheel brakes on can result in front brake overheating and reduced service life.
The retarder lever can be used for all normal braking, as well as to hold the truck at a constant speed on long downgrades. The retarder system provides more accurate downgrade control than the service brake pedal. The front brake valve can be left on when using the retarder control. All four wheel brakes will then be immediately available with the foot pedal in event of an emergency. Avoid engaging and disengaging the retarder continuously. Make adjustments only as necessary to maintain proper R.P.M. and safe, steady speed during retarding.
On slippery roads, use the retarder lever to control the speed. Leave the front brake switch on. Tap foot brake to apply additional braking effort if truck starts to skid.
Ground Speed-must be safe for conditions, at a rate that won't cause brake overheating. Engine Speed-must be at least 1700 R.P.M. to circulate sufficient brake cooling oil through the oil cooler to keep the rear disc brakes cool.
Engine overspeed may cause serious damage. Keep the tachometer indicator in the green operating range.
Brake Oil Temperature-observe the brake oil temperature gauge frequently. If the indicator enters the red zone, the oil cooler capacity has been exceeded. Stop the truck. Run the engine at moderate speed until the oil cools. Then proceed at a slower speed in a lower gear. If the truck gains too much speed while retarding, threatening engine overspeed, use the service brake, in addition to the retarder, until speed is reduced. The retarder system provides less than 100% rear braking, reducing potential wheel lock up.The service brake pedal applies 100% rear wheel braking. Front brakes may also be used