Reusability of Rear Final Drive Splines on 769 to 784 Off-Highway Trucks{3259, 4050, 4051} Caterpillar

Off-Highway Truck/Tractor:

768B (S/N: 79S1-UP)

768C (S/N: 02X1-UP)

769 (S/N: 99F1-UP; 35W1-UP)

769B (S/N: 99F1-UP)

769C (S/N: 01X1-UP)

769D (S/N: BBB1-UP; 5TR1-UP; 5SS1-UP)

770 (S/N: BZZ1-UP)

772 (S/N: RLB1-UP; 10S1-UP; 11S1-UP; 80S1-UP)

772B (S/N: 64W1-UP)

773 (S/N: 63G1-UP)

773B (S/N: 63W1-UP)

773D (S/N: NBJ1-UP; 7ER1-UP; 7CS1-UP)

773E (S/N: BDA1-UP; ASK1-UP)

773F (S/N: EED1-UP)

776 (S/N: 14H1-UP; 14W1-UP)

776B (S/N: 6JC1-UP)

776C (S/N: 2TK1-UP)

776D (S/N: 5ER1-UP; AFS1-UP)

777 (S/N: 84A1-UP)

777B (S/N: 4YC1-UP)

777C (S/N: 4XJ1-UP)

777D (S/N: AGC1-UP; FKR1-UP; 3PR1-UP; 2YW1-UP; AGY1-UP)

777F (S/N: JRP1-UP; JXP1-UP)

777G (S/N: TNM1-UP; RDR1-UP)

784B (S/N: 5RK1-UP)

784C (S/N: 2PZ1-UP)

Quarry Truck:

771C (S/N: 3BJ1-UP)

771D (S/N: BCA1-UP; 6JR1-UP; 6YS1-UP)

773G (S/N: MWH1-UP; JWS1-UP)

775B (S/N: 7XJ1-UP)

775D (S/N: 6KR1-UP)

775E (S/N: BEC1-UP)

775F (S/N: DLS1-UP)

775G (S/N: RFM1-UP; MJS1-UP)

Introduction

© 2012 Caterpillar All Rights Reserved. This guideline is for the use of Cat Dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law.

This Reuse and Salvage Guideline contains the necessary information in order to allow a dealer to establish a parts reusability program. Reuse and salvage information enables Caterpillar dealers and customers to benefit from cost reductions. Every effort has been made in order to provide the most current information that is known to Caterpillar. Continuing improvement and advancement of product design might have caused changes to your product which are not included in this publication. This Reuse and Salvage Guideline must be used with the latest technical information that is available from Caterpillar.

For questions or additional information concerning this guideline, submit a form for feedback in the Service Information System. In order to address an urgent issue, use the following resources in order to communicate your request to Caterpillar Repair Process Engineering:

• Caterpillar Dealer Technical Communicator

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Canceled Part Numbers and Replaced Part Numbers

This document may include canceled part numbers and replaced part numbers. Use NPR on SIS for information about canceled part numbers and replaced part numbers. NPR will provide the current part numbers for replaced parts.

Summary

This guideline provides procedures to evaluate final drive splines for reusability on 769, 771, 772, 773, 775, 776, 777, and 784 Off-Highway Trucks (OHT). Specifications are provided for rear wheel stations.

Splines are used to transmit large amounts of torque. When splines are used, stress concentration is moderate. However, if the splined connection has unacceptable wear, fatigue cracks, or misalignment, high levels of stress may exist. If high stress exists, sudden, premature failure of the spline may result. Therefore, thoroughly evaluate the spines during every rebuild.

Spindle spline life is directly affected by the fit of the wheel bearings. After many hours of heavy-duty operations, enough wear can take place between the wheel bearing cones and spindles/axles to prevent proper wheel bearing adjustment. See Illustration 1. Therefore it is necessary to maintain and repair the bearing diameters in order to extend spline life.

Illustration 1	g02328513
Spindle (1) Bearing journal locations

This guideline contains the latest engineering standards which will help minimize owning and operating costs. When used in the same application, parts that meet the "Use again" specifications in this guideline can be expected to give normal performance until the next scheduled overhaul. Never install a part that this guideline shows "Do not use again". During reconditioning, correct any condition that might have caused the original failure.

References

ReferenceReuse And Salvage Guidelines, SEBF8083, "Inspection and Salvage of Wheel Spindles for all Off-Highway Trucks"

ReferenceReuse and Salvage Guidelines, SEBF9238, "Fundamentals of Arc Spray for Reconditioning Components"

ReferenceReuse and Salvage Guidelines, SEBF9240, "Fundamentals of Flame Spray for Reconditioning Components"

ReferenceReuse and Salvage Guidelines, SEBF9236, "Fundamentals of HVOF Spray for Reconditioning Components"

Tooling and Equipment

The list of machines and tooling is a recommended list.

Cleaning Recommendations

Components should be cleaned prior to inspection. The surface must be free from rust, grease, oil, and burrs that can mask the indications of unacceptable defects.

• Before a part is inspected, clean the part thoroughly to remove all debris, paint, and oil.

• When lifting or moving parts to be cleaned, use proper lifting devices to provide for operator safety, and to prevent part damage.

• During cleaning, do not damage machined surfaces.

• Use pressurized air to dry parts.

• If inspection is not done immediately after cleaning, put hydraulic oil on all machined surfaces to prevent rust or corrosion. Carefully store the parts in a clean container.

Inspection

General Guidelines

The final drive components must be inspected prior to reuse and any salvage repair. Final drive splines are subject to high loads, therefore accurate inspection essential. Splines should be inspected immediately after removal and cleaning. If not, put hydraulic oil on each machined surface to prevent rust or corrosion.

Always use proper lifting devices for operator safety and to prevent machined surface damage. The operator should wear safety glasses at all times as a safety measure.

Failure Progression

The key element to analyzing damage on final drive splines is determining if the damage will progress to a failure before the next overhaul. Analyze the application of the machine, the amount of wear present, and spline size when making this determination.

There are two typical failure progressions:

1. Spline wear or misalignment fracture

2. Fatigue cracking due to fracture

Wear and Misalignment

Spline wear is the result of relative motion between mating spline teeth. High loading, insufficient lube, vibration, and abrasives are a few of the causes. Typically, Off-Highway Truck (OHT) final drive splines can be reused if less than 0.2 mm (0.01 inch) wear step exists. Refer to the reuse dimension tables, Table 3 through Table 17, respectively.

When spline wear is excessive, joint movement increases causing misalignment and imbalance increasing the rate of spline destruction. Excess clearance between splines will also create shock loading during speed, load, and/or direction changes.

There is normally a small amount of relative motion between mating spline teeth. Uneven contact patterns on spline teeth are the result of misalignment of one or both of the mating splines. When the spline teeth are misaligned, teeth are no longer fully engaged. This means that only a portion of each tooth is carrying the full load. Misalignment of teeth causes high contact pressures on the portion of the tooth carrying the load. Thus, surface damage associated with high contact pressures and relative movement will be seen as spline wear in the form of fretting. Misalignment can be identified by the uneven contact pattern on the spline teeth.

Misalignment can be caused by worn or damaged bearings or shafts. If any spline displays uneven contact patterns, be sure to check for misalignment and correct the problem.

Splines with misalignment can be USED AGAIN as long as the wear does not exceed the reuse specifications.

Fatigue Cracks

Numerous broken spline teeth may be the result of bending fatigue failure. The operational loads create tensile stress in the fillet area on the loaded side of the tooth. With enough high loads and cycles, these stresses can cause fatigue cracks. After a fatigue crack develops, the crack will continue to progress until the tooth is sufficiently weakened and separates from the parent metal. Cracking can also occur between the root of the tooth and a bolt hole or inside diameter of the part.

Visual Inspection

Splines can be visually inspected with the naked eye. To provide the best inspection results, a magnifying lens and a strong light source (sunlight is best) is recommended. Small cracks and small scratches may be difficult to distinguish. In these cases, use a liquid magnetic particle inspection system or a dye penetration system.

Be sure to inspect EVERY spline. If a damaged spline is found, all mating splines and splines 180 degrees from the damaged spline should be reinspected for possible bending fatigue, cracks, and wear.

Illustration 2	g02328673
Checking the splines using a seal pick. (2) Seal pick

Splines may need to be measured before reuse if the seal pick stops as the pick is pushed across the worn splines. Generally, a 0.152 mm (0.0060 inch) wear step will stop a seal pick.

Illustration 3	g02328674
Evaluating the splines with steel straight edge and feeler gauge.

If possible, use a steel straight edge and feeler gauge to measure questionable splines. If the measurement is close to the maximum/minimum reuse specification, complete the measurement over pins procedure. Refer to the section ""Spline Wear Limit Evaluation - Measuring Procedure" " in this guideline.

Reusability Examples

Normal Wear

Illustration 4	g02328693

The internal spline with full contact and even wear (refer to Illustration 4). Use again.

Illustration 5	g02328694

The spline shows signs of even loading and full contact (refer to Illustration 5). Use again.

Illustration 6	g02330715
(3) Deep Indentation

Spline has a deep indentation but no signs of cracking (refer to Illustration 6). Use a polishing stone to smooth any sharp edges on the indention. Use again.

Illustration 7	g02330717

Use again the spline, which has external wear step, but meets "Use again" specifications. Fretting corrosion is also apparent due to lack of lubrication, but not to an extent detrimental to reuse. Refer to Illustration 7.

Illustration 8	g02330718
(4) Spline tooth missing

Spline tooth missing and adjacent splines are heavily damaged (refer to Illustration 8). Do not use again.

Illustration 9	g02330719
(5) Cracked spline

Spline is cracked in the root area and crack has progressed into the adjacent splines (refer to Illustration 9). Do not use again.

Pitting and Fretting

Illustration 10	g02330753

The heavy pitting will progress to spalling. Do not use again.

Illustration 11	g02330755

Heavy fretting corrosion will progress to spalling. Do not use again.

Illustration 12	g02330756

Wear step is visible. A 0.152 mm (0.0060 inch) wear step is required to stop a seal pick. Refer to Illustration 12.

Do not use again. If the wear step is greater than the allowable reusability criteria.

Use a seal pick as a "Go-No Go" gauge. Do not use again the component, If the wear step stops the seal pick until the splines are measured. Refer to the ""Spline Wear Limit Evaluation - Measuring Procedure" " section in this manual.

Illustration 13	g02330794
Checking the ends of spline engagement.

Check the ends of spline engagement. Do not use again, If the splines are not worn evenly, check for alignment problems and measure splines prior to reuse. Refer to Table 3 through Table 17 for the reuse specifications.

Note: The reuse specifications presented in Table 3 through Table 17 are based on allowable wear limits developed by Caterpillar Design Engineers. Evaluation of field performance data is on-going and may result in the revision of these specifications in future guideline revisions.

Fatigue Cracks - Spindles

Illustration 14	g02330834
(5) Crack

Crack extending from spline into the bolt hole. The bolt hole strength is compromised and premature, sudden failure may result. Do not use again.

Illustration 15	g02330835
(5) Crack

Crack extends from the root of tooth to inside diameter of part. Tooth failure may result due to high tensile stresses in the tooth root. Do not use again.

Spline Wear Limit Evaluation - Measuring Procedure

Illustration 16	g02330855
(A) Typical wear step on an external spline.

Illustration 17	g02330856
(B) Typical wear step on an internal spline.

The pins used in these inspection procedures must be machined for each individual spline, set according to specified dimensions. Pins should be machined from SAE1020 steel and processed through a magnetizing operation (allows the pins to stay in place during inspection). To perform the inspection on all spline sets covered in this guideline, will require 16 sets of pins. Care must be taken to precisely machine these pins to specification due to the close tolerances of the pin diameters.

Use the following procedure to determine allowable spline wear.

1. Determine the wear on each spline using an inside or an outside micrometer depending on the spline being inspected. To obtain accurate results, the individual performing the check must have a thorough working knowledge of the use of both inside and outside micrometers.

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Illustration 18	g02330893
Pins retained in position (6) Pin

2. Place the pins at 60 degree intervals. The pins should be magnetized or retained by a rubber band to prevent movement .

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Illustration 19	g02330896
Internal spline measurement with pins at 60 degree intervals. Take measurements between pins located 180 degrees apart as indicated. (C) 60 degree

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Illustration 20	g02330902
External spline measurement with pins at 60 degree intervals. Take measurements between pins located 180 degrees apart as indicated. (C) 60 degree

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Illustration 21	g02333936
Measuring the highest two points of the pins (7) Outside micrometer

3. The micrometer must be positioned to measure the highest external and internal two points on the pins. This measurement will provide the wear reading on the spline. The pin diameter for each individual part is specified in that particular procedure. The measurement over pins must be taken every 60 degrees and the readings are added and divided by three. The maximum high/low pin reading must also be determined because the out of round measurement will cause poor load distribution on the spline teeth.

Measurement Examples

Internal Spline

Place pins at 60 degree intervals on the component. The location of the pins at 60 degree intervals is critical to the formula. These three locations will provide information on the wear of the part.

Illustration 22	g02333956
Measurement locations (D) Distance 424.0354 mm (16.69427 inch) (E) Distance 423.8954 mm (16.68876 inch) (F) Distance 424.0042 mm (16.69305 inch)

For example purposes only, Step 1 through Step 4 demonstrates the calculations required to check the measurements of an internal spline at 60 degree intervals. The specifications used in this example are for a 9M-3860 Ring Gear . Refer to Table 4 for the specifications.

1. Take measurements at the locations as shown in Illustration 22. These measurements were as follows:

   (D) = 424.0354 mm (16.69427 inch)

   (E) = 423.8954 mm (16.68876 inch)

   (F) = 424.0042 mm (16.69305 inch)

2. Once all three readings are obtained, add the readings, (D) + (E) + (F) = 1271.9350 mm (50.07608 inch).

3. Now divide the result by three to obtain the average, 1271.9350÷3 mm (50.07608÷3 inch) = 423.9783 mm (16.69203 inch). This calculated dimension is less than the "Reuse Specification Over Pins" of 424.5805 mm (16.71573 inch) and passes this requirement.

4. The difference between the high and the low measurements gives an indication of whether the splines are out of round, which can cause uneven load distribution on the splines. Take the high measurement, 424.0354 mm (16.69427 inch) and low measurement, 423.8954 mm (16.68876 inch) and calculate the difference. The difference between the two measurements also determines if the spline can be used again.

   424.0354 - 423.8954 mm (16.69427 - 16.68876 inch)

   = 0.1400 mm (0.00551 inch)

   Table 4 designates a maximum difference between high/low of 0.8475 mm (0.03337 inch) and the actual difference of 0.1400 mm (0.00551 inch) is less than the allowable maximum. The actual difference is less than the allowable maximum, Use again the spline.

   If the maximum difference between high/low exceeded 0.8475 mm (0.03337 inch), the splined component would be elliptical. Do not use again the spline.

   Note: Both the "Reuse Specification Over Pins" and "Maximum Specification Between High/Low " calculations must be within the specifications given. If the part does not meet both specifications, Do not use again the part.

External Spline

Place pins at 60 degree intervals on the component. The location of the pins at 60 degree intervals is critical to the formula. These three locations will provide information about the wear of the part.

Illustration 23	g02333996
Measurement locations (G) 235.6250 mm (9.27656 inch) (H) 235.4342 mm (9.26904 inch) (J) 235.2113 mm (9.26027 inch)

For example purposes only, Step 1 through Step 4 demonstrates the calculations required to check the measurements of an external spline at 60 degree intervals. The specifications presented in this example are for a 152-8882 Spindle . Refer to Table 9 for specifications.

1. Take measurements at the locations as shown in Illustration 23. These measurements were as follows:

   (G) = 235.6250 mm (9.27656 inch)

   (H) = 235.4342 mm (9.26904 inch)

   (J) = 235.2113 mm (9.26027 inch)

2. Once all three readings are obtained, add the readings, (G) + (H) + (J) = 706.2705 mm (27.80587 inch).

3. Now divide the result by three to obtain the average, 706.2705÷3 mm (27.8060÷3 inch) = 235.4235 mm (9.26862 inch). This calculated dimension is greater than the "Reuse Specification Over Pins" of 235.4024 mm (9.26779 inch) and passes this requirement.

4. The difference between the high and the low measurements gives an indication of whether the splines are out of round, which can cause uneven load distribution on the splines. Take the high measurement, 235.6250 mm (9.27656 inch) and low measurement, 235.2113 mm (9.26027 inch) and calculate the difference. The difference between the two measurements also determines if the spline can be used again.

   235.6250 - 235.2113 mm (9.27656 - 9.26027 inch)

   = 0.4137 mm (0.01629 inch)

   Table 9 designates a maximum difference between high/low of 0.2356 mm (0.00928 inch) and the actual difference of 0.4137 mm (0.01629 inch). The actual difference is more than the allowable maximum, Do not use again the spline.

   Note: Both the "Reuse Specification Over Pins" and "Maximum Specification Between High/Low " calculations must be within the specifications given. If the part does not meet both specifications, Do not use again the part.

Specifications and Location of Spline Sets

Illustration 24 shows the spline sets used on Caterpillar 769, 771, 772, 773, 775, 776, and 777 Off-Highway Trucks. The matching final drive spline sets are identified.

769, 771, 772, 773, 775, 776, and 777 Spline Sets and Specifications

Illustration 24	g02334061
Spline set nomenclature for 769 through 777 final drive. (1) Axle shaft to sun gear (2) Spindle to hub (3) Hub to ring gear

Specifications and Location of Spline Sets

Illustration 25 shows the spline sets used on Caterpillar 784 Off-Highway Trucks. The matching final drive spline sets are identified.

784 Spline Sets and Specifications

Illustration 25	g02337276
Spline set nomenclature for 784 final drive (1) Axle shaft to adapter (2) Spindle to hub (3) Hub to ring gear (4) Ring gear to ring gear (5) Adapter to sun gear (6) Carrier to sun gear

Axle Shaft End Wear

Axle shaft end wear may result due to contact between the axle shaft and the thrust adapter. If end wear has occurred, buff the wear areas with a 4C-3868 Abrasive Disc and a die grinder. The abrasive disc will remove most of the scoring from the axle end and Outer Diameter (OD) with little stock removed. Buffing worn areas smooth will prohibit further wear to the thrust adapter.

Once the axle shaft end and OD have been buffed, measure the shaft. The axle shaft must meet the specifications presented in Illustration 26 through Illustration 32 and Table 11 through Table 17.

769 and 771 Axle Shaft Specifications

Illustration 26	g02337461
7D-7604 and 7D-7605 Axle Shaft (D) 74.549 ± 0.076 mm (2.9350 ± 0.003 inch) dia. (E) 71.755 ± 0.127 mm (2.8250 ± 0.0050 inch) dia. (F) 74.422 mm (2.930 inch) dia.

For length dimensions refer to Table 12.

Illustration 27	g02337463
7D-4854 Axle Shaft 7D-4985 Axle Shaft 9M-4489 Axle Shaft 9M-4490 Axle Shaft 5D-6470 Axle Shaft (D) 74.930 ± 0.127 mm (2.9500 ± 0.0050 inch) dia. (E) 71.425 ± 0.203 mm (2.8120 ± 0.0080 inch) dia. (F) 78.105 mm (3.0750 inch) dia.

For length dimensions refer to Table 11.

772, 773, and 775 Axle Shaft Specifications

Illustration 28	g02338876
7D-7706, 7D-7707, 308-3242, and 308-3243 Axle Shaft (D) 79.324 ± 0.076 mm (3.1230 ± 0.0030 inch) dia. (E) 76.530 ± 0.127 mm (3.0130 ± 0.0050 inch) dia. (F) 79.324 mm (3.1230 inch) dia.

For length dimensions refer to Table 13 through Table 15.

Illustration 29	g02338877
7D-5282 and 7D-5283 Axle Shaft (D) 55.067 ± 0.127 mm (2.1680 ± 0.0050 inch) dia. (E) 127.000 mm (5.0000 inch) dia.

For length dimensions refer to Table 14.

776 and 777 Axle Shaft Specifications

Illustration 30	g02340716
8X-7947 Axle Shaft 8X-7948 Axle Shaft 126-8156 Axle Shaft (D) 75.08 ± 0.15 mm (2.956 ± 0.006 inch) dia. (E) 74.55 ± 0.08 mm (2.935 ± 0.003 inch) dia. (F) 71.76 ± 0.13 mm (2.825 ± 0.005 inch) dia. (G) 69.9 ± 0.5 mm (2.75 ± 0.02 inch) dia. (H) 78.79 ± 0.15 mm (3.102 ± 0.006 inch) dia.

For length dimensions refer to Table 16.

Illustration 31	g02340717
9D-2441 and 9D-2442 Axle Shaft (D) 74.549 ± 0.076 mm (2.9350 ± 0.0030 inch) dia. (E) 71.755 ± 0.127 mm (2.8250 ± 0.0050 inch) dia. (F) 69.85 mm (2.750 inch) dia.

For length dimensions refer to Table 16.

784 Axle Shaft Specifications

Illustration 32	g02340718
2A-7058 and 2A-7206 Shaft (D) 83.56 ± 0.15 mm (3.290 ± 0.006 inch) dia. (E) 74.0 ± 0.5 mm (2.91 ± 0.02 inch) dia. (F) 65.00 ± 0.13 mm (2.559 ± 0.005 inch) dia. (G) 63.32 ± 0.13 mm (2.493 ± 0.005 inch) dia with 2 1/2-12-2ATHD. (H) 57.0 ± 0.5 mm (2.24 ± 0.02 inch) dia. (J) 1.5 ± 0.5 mm (0.06 ± 0.02 inch) × 45 degree.. (K) 76.53 ± 0.13 mm (3.013 ± 0.005 inch) dia. (L) 79.32 ± 0.08 mm (3.123 ± 0.003 inch) dia.

For length dimensions refer to Table 17.

Repair Procedures

Front and Rear Spindle Repair

Spindle spline life is affected by the fit of the wheel bearings. Therefore it is necessary to maintain/repair the bearing diameters in order to extend spindle life. Deterioration of a bearing diameter will cause the spindle to wear along with other mating parts.

Refer to Reuse And Salvage Guidelines, SEBF8083, "Inspection and Salvage of Wheel Spindles for all Off-Highway Trucks", for specific information related to spindle repair.

Metal Spray Technologies

Metal spray technologies are an acceptable salvage method for bearing surface repair. Each step in the metal spray process is critical in achieving the desired coating, bond, and surface finish. Refer to Reuse and Salvage Guidelines, SEBF9238, "Fundamentals of Arc Spray for Reconditioning Components", Reuse and Salvage Guidelines, SEBF9240, "Fundamentals of Flame Spray for Reconditioning Components", or Reuse and Salvage Guidelines, SEBF9236, "Fundamentals of HVOF Spray for Reconditioning Components" for additional information about metal spray repair procedures.