TUBE AS 8W4552 - Caterpillar

651B, 657B Tractor-ScrapersDescription of Change: New brake actuators are used on 641B, 651B and 657B Tractor-Scrapers. The new actuators use spring force for parking and emergency brake application, and are held in the released position by system air pressure during normal machine operation. Service brake application is the same as before, with air pressure controlled by the brake pedal valve. With the use of spring force for parking and emergency brake application, the circuit for the air-operated emergency system is not needed. This permits a new design of the air and brake control with less parts. The new brake system will also prevent possible problems with the parking brake. The parking brake formerly used was some times difficult to disengage (release).
Adaptable To: All earlier 641B, 651B and 657B Tractor-Scrapers. Because of the number of parts needed, a field conversion group will be made available, with a special instruction form for installation. Information about this group and the special instruction will be published as soon as possible.