1998/09/28 Caterpillar

777B (4YC, 3NF),
777C (4XJ),
777D (3PR, 2YW),
783B (8YM),
785 (8GB),
785B (6HK),
785C (5AZ, 1HW) 789 (9ZC),
789B (7EK),
789C (2BW),
793 (3SJ),
793B (1HL),
793C (4AR, 4GZ) Off-Highway Trucks;
776B (6JC),
776C (2TK),
776D (5ER),
784B (5RK) Off-Highway Tractors;
854G (1JW) Wheel Tractors;
D11N (74Z, 4HK),
D11R (8ZR, 9TR, 9XR) Tractors;
992G (7HR),
994 (9YF) Wheel Loaders;
5130 (7TJ, 5ZL),
5130B (4CS),
5230 (7LL) Excavators

Description of Change: A new gear and new shaft assemblies are used in the scavenge oil pumps on the 3500 Engines in these machines. The former gear created a stress riser on the shaft assembly. See Illustration 1. This stress riser could cause the shaft to break. The new gear and the new shaft assemblies have been designed so that the edge of the gear no longer contacts the shaft. See Illustration 2. This eliminates the potential for a stress riser.

Adaptable To: Chart A identifies the new and former components in the scavenge oil pump groups on the 3500 machine engines in the above machines. Chart B identifies the scavenge oil pump serial numbers when the new components became effective. Chart C identifies the machine and engine effectivity of the new components.

Illustration 1.

Former shaft assembly (A).

Former gear (B).

Bolt that fastens the gear to the shaft assembly (C).

Area of contact between former shaft assembly and edge (X) of former gear.

Illustration 2.

New shaft assembly (D).

New gear (E).

Bolt that fastens the gear to the shaft assembly (C).

Edge (Y) of new gear does not contact new shaft assembly.