1997/05/19 Caterpillar

784B (5RK) Tractors, 785 (8GB),
785B (6HK),
789 (9ZC),
789B (7EK),
793 (3SJ),
793B (1HL),
793C (4AR) Off-Highway Trucks

Reference: Service Magazine; October 18, 1993; Page 6; "Bearings Are Used to Prevent Seizure of Rear Suspension Cylinder Pins".

Description of Change: A new locking mechanism is now used on rear suspension cylinder bearing pins to prevent bearing pin rotation within rear axle housing and truck frame bearing bores. The new anti-rotation pin will increase service life of bearings between the pins and bearing bores.

Also, New bearing lubrication lines are now used on rear suspension cylinders to allow for improved lubrication of rear suspension pins and bearings. The bearing lubrication lines are mounted on the inboard face of the bearing journal to prevent hose damage from falling debris.

Antirotation Pins

Illustration 1. Typical view of 3T-1208 Block welded to truck frame. [Illustration is inverted for 3T-1208 Block welded to axle housing (B)].
(A) 3T-1208 Block. (AA) 77 ± 3 mm (3.03 ± .12 in). (BB) 50 ± 3 mm (1.97 ± .12 in). (W) 12.0 mm (.47 in) fillet weld, 1.5 mm (.06 in) penetration, 3 sides only.

Adaptable To: Two 3T-1208 Bars (A) are now welded to the rear axle housing assembly and two are welded to the frame assembly as shown in Illustration 1. In addition to the changes listed below, This change is effective with and adaptable to all off-highway trucks as follows:

Changes To 784B (5RK) Tractors, 785 (8GB), And 785B (6HK) Off-Highway Trucks

In addition to changes listed in Chart 1, the 2J-3505 Nut has been removed from 2A-6987 Suspension Group effective with 784B (5RK23) Tractor and adaptable to 784B (5RK1-22) Tractor; and from 5T-0884 Suspension Group effective with 785B (6HK638) Off-Highway Truck and adaptable to 785 (8GB1-Up) and 785B (6HK1-637) Off-Highway Truck.

NOTE: For all 785B (6HK1-100), this change is only adaptable to trucks which have been serviced to include 7I-5494 Bearing as described in the service magazine article referenced at the beginning of this article.

Changes To 789 (9ZC), 789B (7EK) Off-Highway Trucks

In addition to changes listed in Chart 2, four 2J-3507 Nuts and four 5P-8520 Hard Washers have been removed from 5T-4466 Suspension Group effective with 789B (7EK498) Off-Highway Truck. This change is adaptable to 789 (9ZC1-Up) and 789B (7EK1-497) Off-Highway Trucks.

NOTE: For all 789B (7EK1-110), this change is only adaptable to trucks which have been serviced to include 8X-8654 bearing as described in the service magazine article referenced at the beginning of this article.

Changes To 793B (1HL), 793C (4AR) Off-Highway Trucks

In addition to changes listed in Chart 3, twelve 6V-3531 Bolts and twelve 8T-3282 Hard Washers have been removed from 8X-2793 Suspension Group effective with 793C (4AR80) Off-Highway Trucks and adaptable to all 793 (3SJ1-Up), 793B (1HL1-Up) and 793C (4AR1-79) Off-Highway Trucks.

NOTE: For all 793 (3SJ1-36) and 793B (1HL1-11) Off-Highway Trucks, this change is only adaptable to trucks which have been serviced to include 8X-8654 bearing as described in the service magazine article referenced at the beginning of this article.

Inboard Lubrication Lines

Changes For 784B (5RK) Tractors, 785 (8GB), 785B (6HK), 789 (9ZC), And 789B (7EK) Off-Highway Trucks

Illustration 2. Typical view of automatic lubrication group. See Chart 4 for list of components.

Adaptable To: Parts listed in Chart 4 have been added to the following lubrication groups:

* 2A-6729 Automatic Lubrication Group effective with 784B (5RK23) Tractor. This change is adaptable to 784B (5RK1-22) Tractor.

* 8X-8260 Automatic Lubrication Group effective with 785B (6HK638) Off-Highway Truck. This change is adaptable to all 785B (6HK102-637) Off-Highway Trucks, and to all 785 (8GB1-Up) and 785B (6HK1-101) Off-Highway Trucks which have bearings installed in rear suspension cylinder mounting bores.

* 8X-8270 Automatic Lubrication Group effective with 789B (7EK497) Off-Highway Truck. This change is adaptable to all 789B (7EK112-496) Off-Highway Trucks, and to all 789 (9ZC1-Up) and 789B (7EK1-111) Off-Highway Trucks which have bearings installed in rear suspension cylinder mounting bores.

The following additional changes to 8X-8260 and 8X-8270 Automatic Lubrication Groups are also effective with and adaptable to the models listed above.

The 5T-4385 Hose Assembly directly replaces 5T-4386 Hose Assembly previously used in 8X-8260 Automatic Lubrication Group.

The 8L-6557 Connector directly replaces 2N-1287 Elbow previously used in 8X-8270 Automatic Lubrication Group. The 6V-1813 Nipple and 8B-4884 Elbow have been removed also.

Changes For 793 (3SJ), 793B (1HL), 793C (4AR) Off-Highway Trucks

Illustration 3. View of central grease lines group. See Chart 5 for list of components.

Parts listed in Chart 5 have been added to 125-4975 Grease Lines Group effective with 793C (4AR116). This change is adaptable to all 793C (4AR1-116), 793B (1HL12-Up), 793 (3SJ37-Up) Off-Highway Trucks; and to all 793B (1HL1-11) and 793 (3SJ1-36) which have bearings installed on rear suspension cylinder mounting bores.