1994/07/18 Caterpillar

Improved Back-up Rings Prevent Pressure Build-up In Off-highway Truck Hoist Cylinder Groups{5102}

Usage:

769C (01X, 1ED),
773B (5SC, 63W),
777 (84A),
777B (4YC),
777C (4XJ),
785 (8GB),
785B (6HK),
789 (9ZC),
789B (7EK),
793 (3SJ),
793B (1HL) Trucks;
771C (3BJ),
775B (7XJ) Quarry Trucks

Improved back-up rings that have notches are available for use in off-highway truck and quarry truck hoist cylinders. The new back-up rings with the notches will prevent pressure build-up in the hoist cylinders. The former back-up rings would allow pressure to build between the ring seals and back-up rings causing them to extrude.

If a machine has hoist cylinder seals and back-up rings which show signs of extrusion, replace the damaged seals and install new back-up rings with notches. The hoist cylinder groups and back-up ring part numbers are shown in the chart.

Typical back-up ring location.

NOTE: Only the part numbers for the back-up rings used in 789B and 793B Off-highway Trucks have changed. The new back-up rings are a direct replacement for the former back-up rings.

Caterpillar Information System:

1994/07/18 New Cam Adjustable Link Now Used With Motor Grader Rippers{6166}

1994/07/18 Air Ride Seat Suspension Retrofit{7307}

1994/07/11 Intake And Exhaust Valve Lash Increased{1105}

1994/07/11 Different Fuel Filter Available To Prevent Premature Wear On Fuel Injection Pump Plungers And Barrels{1261,1251}

1994/07/11 Bulk Hose Material Is Available For Air Conditioners With R-134a Refrigerant{1808}

1994/07/11 New Hose Assemblies Used In Turbocharger Oil Lines Groups{1307}

1994/07/11 New Vibratory Pump Components Improve Service Life{5070}

1994/07/11 Throttle Cable Improved{1265}

1994/07/11 New Vibratory Drive Shaft Improves Service Life{6645}

1994/07/11 Cover Required To Adapt New Windshield Washer Motor{7306}

1994/07/11 New Pilot Operated Relief Valve Group Improved To Prevent Relief Spool Sticking{5072}

1994/07/11 New Gasket Used On Separate Circuit Aftercooler (SCAC) Radiator Inlet Elbow{1353,1380}

1994/07/18 New Instrument Panel Groups With Improved Light Bulb Retention Can Be Installed{7451}

1994/07/18 Diameter Of Spherical Bearings In Steering Cylinders Increased{7072,4303}

1994/07/18 Rubber Drive Belt Field Repair Kit{4213}

1994/07/25 Lubrication Oil Recommendations Have Been Changed For Caterpillar OFF-Highway Trucks And Tractors{0374,0375}

1994/07/25 Correct Position Of Clamp Assembly Is Required To Prevent Tie Rod Damage{4318,4329}

1994/07/25 Maintenance Interval For Steering Components, Hoist Cylinder Bearings And Rear Axle Housing "A" Frame Bearings Has Changed{7521,7551}

1994/07/25 Spacers Used To Eliminate Noise Due To Lateral Hoist Cylinder Movement When The Body Is Raised{5102}

1994/07/25 A New SEPD0208 Special Edition Service Magazine Available For "D" Series Articulated Trucks{0374}

1994/07/25 New Locking Plate And Thrust Flange Used In Hitch Drive Shaft Group{7051}

1994/08/08 New Front Engine Support Available For Parts Service{1153}

1994/08/08 External Fuel Tank Wear And Corrosion Can Be Prevented{1273}

1994/08/08 Body Mounting Plate Can Contact Front Service Brake Roto Chamber{4262,4266,7258}