1996/05/20 Caterpillar

784B (5RK) Tractors;
785 (8GB),
785B (6HK),
789B (7EK) Trucks

Reference: Service Magazine; June 27, 1994; Page 14; "New Assembly Procedure For Hydraulic Pump Groups With Double Shaft Seals And A Weep Hole Between The Seals Helps Prevent Contamination Through The Weep Hole".

New service parts and new assembly procedure prevent leaking shaft seals, provide early visual detection of hydraulic oil when seal leaks occur, and prevent hydraulic oil from seeping out the weep hole when leaks do not occur.

To prevent seal leakage, or the appearance of seal leakage, the following changes are specified:

* Shaft seals are arranged with spring loaded sides opposite each other.

* A retaining ring replaces the spacer between the shaft seals.

* A porous bronze plug replaces the rubber plug in the weep hole.

NOTE: The new bronze plug lets contaminated oil drain through the weep hole, allowing early detection of shaft seal leakage.

NOTE: Machines having water glycol hydraulic systems are excluded from this procedure.

This change is adaptable to all 4T-2606 Pump Groups in service. See illustration, chart, and procedure to update 4T-2606 Pump Groups.

4T-2606 Pump Group. Reference only: Double shaft seal, new retaining ring, and new arrangement (A); and new bronze plug in weep hole (B). See chart for service parts.

Procedure To Update 4T-2606 Pump Group

1. Remove and save eight existing 7H-3607 Nuts (1) from drive end flange as. (5).

2. Remove and discard eight former 4B-1550 Washers (2).

3. Remove drive end flange as. (5).

4. Remove two 5P-9597 Seals-Shaft (3) and former 3G-7241 Spacer (4) from drive end flange (5).

5. Remove rubber 3G-7242 Plug (6), if in weep hole (B), of drive end flange as. (5).

6. Clean drive shaft of pump and inspect spline and shaft for burrs. Remove burrs if found.

7. Clean and inspect drive end flange as. (5). The weep hole, seal-O-ring groove, and shaft seal counterbore must be clean and free of imperfections.

NOTE: The shaft seal counterbore must be smooth. If the seal surface is scored or has tool marks, install new drive end flange.

8. Install new plug (6). Insert chamfer end first and push flush into weep hole, as shown in detail B.

9. Use 6V-1541 Quick Cure Primer to clean seal counterbore and the OD of the first new seal-shaft (3).

10. Install seal-shaft (3) into drive end flange (5). (Make sure spring loaded member faces pump side, as shown in detail A.)

NOTE: Put three drops of 4C-9506 or 4C-9507 Retaining Compound between seal and counterbore, one at 12:00, one at 4:00, and one at 8:00.

11. Install new ring-retaining (4). (Make sure opening is over weep hole.)

12. Install new seal-o-ring (7) in groove of drive end flange (5).

13. Position drive end flange as. (5) on pump.

NOTE: Be careful not to score shaft seal or let seal lip roll back on shaft when pushing seal past the spline.

NOTE: Be careful not to pinch seal-O-ring or damage balance seals.

14. Install eight new 5P-8247 Washers-Hard (2) and eight existing 7H-3607 Nuts (1). Torque each nut to 238 ± 13 N·m (175 ± 10 lb ft).

NOTE: Bench test pump for integrity of first new shaft seal.

15. Use 6V-1541 Quick Cure Primer to clean OD of second new 5P-9597 Seal-Shaft (3).

16. Install seal-shaft (3). (Make sure spring loaded member faces away from pump side, as shown in detail A.)

NOTE: Be careful not to score shaft seal when pushing seal past the spline.

NOTE: Put three drops of 4C-9506 or 4C-9507 Retaining Compound between seal and counterbore, one at 12:00, one at 4:00, and one at 8:00.

NOTE: Bench test pump for integrity of second new shaft seal.