1997/09/22 Caterpillar

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

SUPPLEMENT: MAY 3, 1999

Service Magazine SEPD0383, Article 13, Page 19, September 22, 1997; "New Differential Pinion Bearing Setting Tool And Procedure Available".

Disregard this article and refer to Service Magazine SEPD0470, Article 12, Page 13 with the title "Corrected Differential Pinion Bearing Setting Tool And Procedure".

--------------- END SUPPLEMENT ---------------

Description of Change:

NOTE: This article replaces Service Magazine article published May 19, 1997; Page 38; "New Differential Pinion Bearing Setting Tool and Procedure Available".

A new differential pinion bearing setting tool is now available. Using the pinion bearing setting tool with the new bearing setting procedure will improve pinion bearing assembly and reliability.

NOTE: Distance measured from the pinion bearing cage face to the carrier housing through the newly machined holes (as indicated in this procedure) is very important to the end play adjustments. The need to spot face the cage face at the lifting eye holes or newly machined holes is NOT necessary to accurately measure and calculate the shim pack if this procedure is used.

Adaptable To: The differential pinion bearing setting tools and bearing setting procedure below can be used for all former 784 Tractor, 785, 789 and 793 Off-Highway Truck differential bevel and gear groups.

NOTE: The procedure below is for all 784 Tractor, 785, 789 and 793 Off-Highway Truck differential bevel and gear groups fitted with the new thick flange 127-0353 Pinion Bearing Cage (field service), or 125-5935 Pinion Bearing Cage.

Pinion Bearing Setting Procedure:

NOTE: Due to the bolt stretch resulting from the new torque turn method, always use new bolts each time you rebuild the pinion heel bearing cage.

NOTE: Use of 8X-0383 Cage with original bolts, loctite and washers (no spacers) is NOT recommended.

1. This procedure requires that bearing cups are fully seated inside the bearing cage and carrier bore. Make sure that the bearing cups and cones are seated against their respective housing and shaft shoulders before assembly of the other components. Verify bearing seating with a piece of 0.003 mm (.002 in.) thick shim stock or a standard feeler gage.

2. Drill and tap 7/16-20 class 2A thread in the pinion bearing cage assembly in the two locations noted to accept the 122-0449 Rod Sleeve Extension. (See Illustration 1 - 793 Truck; See Illustration 2 - 789 Truck; See Illustration 3 - 785 Truck).

Illustration 1. View of pinion bearing cage assembly reworked for 793 Trucks. (AA) 47 mm (1.85 in). (BB) 240 mm (9.45 in). (CC) 0 mm (0 in). (DD) 240 mm (9.45 in). (EE) 47 mm (1.85 in). (FF) 0 mm (0 in).

Illustration 2. View of pinion bearing cage assembly reworked for 789 Trucks. (AA) 125 mm (4.92 in). (BB) 190.08 mm (7.483 in). (CC) 0 mm (0 in). (DD) 190.08 mm (7.483 in). (EE) 0 mm (0 in). (FF) 125 mm (4.92 in).

Illustration 3. View of pinion bearing cage assembly reworked for 785 Trucks. (AA) 55.52 mm (2.186 in). (BB) 0 mm (0 in). (CC) 55.52 mm (2.186 in). (DD) 207.19 mm (8.157 in). (EE) 0 mm (0 in). (FF) 207.19 mm (8.157 in).

Illustration 4. View of pinion gear and pinion cage (arrows) assembled to differential carrier. (a) Transmission case. (b) Banjo housing.

3. Install the pinion gear in the carrier with the axis of the pinion shaft oriented in the vertical position.

4. Place a flat piece of metal under the pinion cage assembly directly below the dial indicator and zero the dial indicators. See Illustration 5.

Illustration 5. View of dial indicator zeroed.

5. Remove the flat piece of metal previously used to zero the dial indicator and assemble the pinion cage assembly, without seals and shims, to the carrier housing. Make sure the bearings are well oiled.

Illustration 6. View of fabricated spacer (arrow). (AA) 57.2 ± 1 mm (2.251 ± .039 in). (BB) 120 mm (4.72 in) dia. max.

6. Fabricate the spacer as shown in Illustration 6.

Illustration 7. View of fabricated pinion drive plate (A). (a1) 25.4x3 mm THK x 100 mm long square tube - 1018 steel, 4 Req'd. (a2) 53.5x100 mm x 3 mm THK plate - 1018 steel, 1 Req'd. (AA) 3 mm (0.12 in) THK. (BB) 100 ± 1 mm (3.94 ± 0.04 in). (CC) 53.5 ± 1 mm (2.11 ± .04 in). (DD) 25.4 mm (1.00 in). (W1) Fillet weld both sides, 3 mm (.12 in) penetration, 4 places.

7. Fabricate the pinion drive plate (A) shown in Illustration 7.

Illustration 8. Setup for differential pinion bearing setting procedure. ¹Use these components for 793 Off-Highway Truck differential bearing setting procedure. ²Use these components for 785 and 789 Off-Highway Truck differential bearing setting procedure.

8. Install the fabricated spacer (not pictured in Illustration 8) and fabricated pinion drive plate (A) into the pinion spline through the center hole as shown in Illustration 8.

NOTE: The fabricated pinion drive plate should rest on top of the fabricated spacer to allow for proper spline engagement depth.

Illustration 9. View of fabricated cap plate (B). (b1) 241.3 mm DIA. x 19 mm THK plate - 1018 steel, 1 Req'd. (a2) 25.4x100 mm x 6.35 mm THK plate - 1018 steel, 3 Req'd. (AA) 6.35 mm (0.25 in). (BB) 120°. (CC) 241.3 ± 1 mm (9.50 ± .04 in) DIA. (DD) 25.4 mm (1.00 in). True position tolerance - 0.5 mm (.020 in) DIA to datum A. (EE) 136.6 mm (5.38 in) DIA. True position tolerance - 0.5 mm (.020 in) DIA to datum A. (FF) 29.4 mm (1.16 in) class B hole. Datum A. (GG) 50.8 ± 0.5 mm (2.000 ± .020 in). (HH) 19 mm (.75 in) THK. (W2) Fillet weld both sides, 3 mm (.12 in) penetration, 3 places.

9. Fabricate the cap plate (B) shown in Illustration 9.

10. Install the fabricated cap plate (B) on top of the pinion bearing cage assembly with the three metal pads in the downward direction as shown in Illustration 8.

11. Place the 1U-7552 30 TON Hydraulic Ram (7) on top of the fabricated cap plate as shown in Illustration 8.

Illustration 10. View of fabricated pinion drive shaft (D). (d1) 28.6 mm (1.125 in) dia., 247.7 mm (9.75 in) long rod. (d2) 12.7 mm (.50 in) x 19.05 mm (.750 in) x 25.4 mm (1.00 in) long block. (W1) 3 mm (.118 in) penetration fillet weld all around, 2 places. (AA) 289.4 mm (11.39 in) ref. (BB) 247.7 ± 1.0 mm (9.75 ± .04 in). (CC) 25.4 ± 1 mm (1.00 ± .040 in). (DD) 152.4 ± 5 mm (6.00 ± .20 in). (EE) 12.7 mm (.50 in). (FF) 19.05 mm (.75 in). (GG) 28.6 mm (1.13 in).

12. Fabricate the pinion drive shaft (D) as shown in Illustration 10.

Illustration 11. View of fabricated sleeve (E). (e1) 19 mm (.75 in) dia. x 13 GA. wall x 222.3 mm (8.75 in) long Tube. (AA) 222.3 mm (8.75 in). (BB) 19 mm (.75 in) dia.

13. Fabricate four sleeves (E) as shown in Illustration 11.

Illustration 12. View of fabricated top plate. (a1) 519 mm (20.43 in) DIA x 19 mm (.75 in) THK plate - 1018 steel. (AA) 210.18 mm (8.27 in). (BB) 130.2 mm (5.13 in). (CC) 107.25 mm (4.22 in). (DD) 93.6 mm (3.69 in). (EE) 87.06 mm (3.43 in). (FF) 185.76 mm (7.31 in). (GG) 225.98 mm (8.90 in). (HH) 225.98 mm (8.90 in). (JJJ) 210.18 mm (8.27 in). (JJ) 185.76 mm (7.31 in). (KK) 11.0 mm (.433 in) class A hole, tap 1/2-13 class 2B THD, 2 holes. True position tolerance - 0.9 mm (.035 in) DIA to datums A and B. (LL) 14 mm (.55 in) class B hole, 12 holes. True position tolerance - 0.9 mm (.035 in) DIA to datums A and B. (MM) 130.2 mm (5.13 in). (NN) 429 mm (16.89 in) DIA. (KKK) 107.25 mm (4.22 in). (PP) 87.06 mm (3.43 in). (QQ) 489 mm (19.25 in) DIA. (RR) 93.6 mm (3.69 in). (SS) 455 mm (17.91 in) DIA. (TT) 519 ± 1 mm (20.43 ± .04 in) DIA. (UU) 29.4 mm (1.157 in) class B hole. Datum A. (VV) 93.6 mm (3.69 in). (WW) 87.06 mm (3.43 in). (LLL) 107.25 mm (4.22 in). (YY) 130.2 mm (5.13 in). (ZZ) 185.76 mm (7.31 in). (AAA) 210.18 mm (8.27 in). (BBB) 225.98 mm (8.90 in). (CCC) 225.98 mm (8.90 in). (DDD) 185.76 mm (7.31 in). (EEE) 87.06 mm (3.43 in). (FFF) 93.6 mm (3.69 in). (GGG) 107.25 mm (4.22 in). (HHH) 130.2 mm (5.13 in). (MMM) 210.18 mm (8.27 in). (NNN) 19 mm (.75 in).

14. Fabricate the top plate (C) as shown in Illustration 12.

15. Insert four 5P-5421 Bolts (5) and 4B-4280 Washers (19) through the fabricated top plate and (C) fabricated sleeves (E). Install two of the bolts, washers and sleeves next to the lifting eye holes 180 degrees apart on the bearing cage. Install the other two bolts, washers and sleeves approximately 90 degrees from the bolts next to the lifting eye holes. (See Illustration 8).

NOTE: Use the hardware above for 785 and 789 Off-Highway Truck differential pinion bearing setting procedure. For 793 Off-Highway Truck setting procedure, substitute two 1U-6343 Threaded Rod (6) sawed in half (four 1/2 m lengths) and four 6V-8149 Nuts (8) for four 5P-5421 Bolts (5) used in Step 15.

16. Fit the 143-6092 Digital Pressure Sensing Unit (14), 1S-8937 Gate Valve (15), the 1P-2376 Couplers (3), 1P-2375 Couplers (2), 8F-0024 Hose Assembly (1), 6V-3966 Nipple (16), 6V-4143 Coupler (17) and 2D-7325 Tee (18) to the 1U-7552 Ram (7) as shown in Illustration 8.

Illustration 13. View of dial indicator assembled to pinion cage assembly.

17. Install the two 6V-6106 Dial Indicators (10) to two 122-0449 Rod Sleeve Extensions (9) in the pinion cage assembly. (See Illustrations 7 and 13).

NOTE: Attach 5P-4160 Contact Point (11) to dial indicator for of 789 and 793 Off-Highway Truck shim thickness measurement. Attach 3S-3269 Contact Point (12) to dial indicator for 785 Off-Highway Truck shim thickness measurement.

18. Without applying 1U-7552 Ram (7) pressure, ZERO the two 6V-6106 Indicators (10) and install the pinion drive shaft (D) as shown in Illustration 12.

19. Apply 2,700 PSI ram pressure and CLOSE the gate valve. Rotate the pinion by turning the pinion drive shaft (D) at least two revolutions.

NOTE: It is critical to rotate the pinion to obtain proper seating of all components. If ram pressure drops during or after rotating the pinion, open the gate valve to increase the pressure to 2,700 PSI and rotate the pinion drive shaft (D) two more revolutions.

20. Repeat Step 19 until pressure is stable after pinion rotation.

21. OPEN the gate valve and relieve pressure to 0 kPa (0 psi).

22. Increase ram pressure to 750 psi and rotate the pinion by turning the pinion drive shaft (D) at least two revolutions.

NOTE: It is critical to rotate the pinion to obtain proper adjustment of this component. If ram pressure drops during or after rotating the pinion, OPEN the gate valve to increase the pressure to 5167.5 ± 103.4 kPa (750 ± 15 psi). Close the gate valve and rotate the pinion drive shaft (D) two more revolutions.

23. Repeat Step 22 until pressure is stabilized after pinion rotation.

24. Record the average measurement from both 6V-6106 Indicators.

25. Assemble shim pack with thickness based on the average measurement recorded in Step 22:

* 785 and 789 Trucks - [Shim = Ave.Measurement + .007 in]

* 793 Trucks - [Shim = Ave.Measurement + .010 in]

26. Disassemble and install seals to the bearing cage. Reassemble bearing cage with the proper shim thickness to the carrier housing.

Illustration 14. Typical view of 785B Truck differential carrier - bearing cage side. Criss-Cross pattern (1), (2), (3), and (4) of tightening the bolts, lifting eye hole #2 (1A), bearing cage assembly (2A), carrier housing (3A), bearing cage flange (4A), and lifting eye hole #1 (5A).

Illustration 15. Typical view of 789B Truck differential carrier - bearing cage side. Criss-Cross pattern (1), (2), (3), and (4) of tightening the bolts, lifting eye hole #2 (1A), bearing cage assembly (2A), carrier housing (3A), bearing cage flange (4A), and lifting eye hole #1 (5A).

Illustration 16. Typical view of 793B Truck differential carrier - bearing cage side. Criss-Cross pattern (1), (2), (3), and (4) of tightening the bolts, lifting eye hole #2 (1A), bearing cage assembly (2A), carrier housing (3A), bearing cage flange (4A), and lifting eye hole #1 (5A).

27. Install all NEW cage bolts and washers without thread sealant. Tighten the cage bolts to 50 ± 5 N·m (36.8 ± 3.8 lb ft). Rotate all bolts an additional 60 ± 5°.

28. Check to make sure the pinion rotates freely.