Service Brakes for Off-Highway Trucks and Tractors {4006, 4008, 4251, 4254, 4255, 4256, 4273} Caterpillar

Off-Highway Truck/Tractor

All

Introduction

Table 1

Revision	Summary of Changes in SEBF8095
11	Added serial numbers.
10	Added new minimum dimension for reuse for linings.
09	Added one part number.

© 2018 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. Information contained in this document is considered Caterpillar: Confidential Yellow.

This Reuse and Salvage Guideline contains the necessary information 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 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 technical questions when using this document, work with your Dealer Technical Communicator (TC).

To report suspected errors, inaccuracies, or suggestions regarding the document, submit a form for feedback in the Service Information System (SIS Web) interface.

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.

Important Safety Information

Illustration 1	g02139237

Follow all safety warnings. Most accidents that involve product operation, maintenance, or repair are caused by failure to observe safety warnings. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. Personnel must be properly trained to perform maintenance, repair, or operate any machine. Safety precautions and warnings are provided this instruction and on Caterpillar products. These warnings should be observed before performing any procedures. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The warnings in this publication and on the product are not all inclusive.

The hazards are identified by the “Safety Alert Symbol” which is followed by a “Signal Word” such as “DANGER”, “WARNING” or “CAUTION”. The “WARNING” Safety Alert Symbol is shown in Illustration 2.

Illustration 2	g00008666

This safety alert symbol means:

Pay Attention!

Become Alert!

Your Safety is Involved.

The message that appears under the safety alert symbol explains the hazard.

Operations that may cause product damage are identified by "NOTICE" labels on the product and in this publication.

Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The safety information in this document and the safety information on the machine are not all inclusive. Determine that the tools, procedures, work methods, and operating techniques are safe. Determine that the operation, lubrication, maintenance, and repair procedures will not damage the machine. Also, determine that the operation, lubrication, maintenance, and repair procedures will not make the machine unsafe.

The information, the specifications, and the illustrations that exist in this guideline are based on information which was available at the time of publication. The specifications, torques, pressures, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Obtain the complete, most current information before you start any job. Caterpillar dealers can supply the most current information.

Summary

Note: This guideline applies only to service brakes on Off-Highway Trucks. The guide provides the reuse examples and criteria to assist dealer technicians in making reuse decisions. Reuse dimensions are also provided.

Table 2

References
Media Number	Title
SEBF8115	Transmission Clutch Plates and Disc Assemblies with Cellulose (Paper) Friction Materials
SEBF8013	Transmission Clutch Plates and Disc Assemblies with Sintered Bronze Friction Material
SEBF8031	Transmission Clutch Plates and Disc Assemblies with F37 Clutch Friction Material
SEBF8225	Reusability of Final Drive Splines Used on 785- 797 Off-Highway Trucks
SEBF8759	Reusability of Final Drive Splines Used on 769- 784 Off-Highway Trucks

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.

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NOTICE
Do not use water, steam, water-based solutions, Freon, paint thinner, or ketones to clean brake discs. Refer to the “Disc Composition and Cleaning” section of this guide for correct cleaning methods.

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NOTICE
Use all cleaning solvents and solutions with care. Wear eye and ear protection when using high-pressure cleaning equipment. Always use cleaning solvents in a well-ventilated area. Always wear protective clothing when using caustic cleaning solutions. Failure to follow the precautions provided by the manufacturer equipment, and/or solvents, can result in bodily injury. Pressurized air can cause personal injury. When using pressurized air for cleaning and drying parts, wear a protective face shield, protective clothing, and protective shoes. The maximum air pressure must be below 200 kPa (30psi).

• 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.

Caliper Type Disc Brakes

Illustration 3	g03697124
Brake Head Assembly (1) Linings (2) Pin (3) Boot (4) Retainer (5) Seals (6) Seals (7) Plug (8) Retainer/Seal grooves (9) Piston (10) Cover (11) Torque Plate

Illustration 4	g03697128
Standard Caliper Disc Front Brakes

Illustration 5	g03697147
Standard Caliper Disc Front Brakes

Standard Caliper Disc Front Brakes

Caliper or dry disc type brakes are used on the 769B through the 775E Off-Highway Truck (OHT). 777 OHT's may be equipped with either standard caliper disc front brakes or oil cooled multi disc front brakes. Refer to Table 5 for a summary of the OHT caliper lining part numbers. Refer to Table 3 for a summary of the OHT caliper disc part numbers.

Inspection Procedures

Inspect the following components during a planned component rebuild or other maintenance.

• Inspect brake periodically to insure that all boots (3) are tight and that there are no leaks. Refer to the appropriate Operation and Maintenance Manual for the service intervals.

• Inspect for boot (3) deterioration.

• Replace all rubber sealing components (3, 5, 6) if the brake head assembly has had an extended use. Otherwise replace damaged parts as needed.

• Inspect carrier and lining assemblies (1). Refer to the section “Lining Wear” in this manual.

• Clean torque plate (11) if corrosion is excessive or if seal grooves are damaged preventing proper reassembly of brake.

• Inspect pistons (9) for minor scratches and nicks. If piston is nicked or scratched or if the chrome plating is worn off, replace piston.

• Replace Torque pins (2) that are grooved or badly worn.

• Check the plug (7) and cover (10) for significant damage and replace as necessary.

Illustration 6	g03697179
Lining Assembly (12) Wear Indicator Grooves (13) Carrier (14) Lining

Lining Wear

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NOTICE
Failure to replace the lining when worn to limits will result in loss of braking and possible catastrophic failure.

Linings must be replaced when they have worn more to 3.15 mm (0.124 inch) of lining material or worn past the wear indicator groove depth (12). Evaluation of the wear indicator groove depth (12) provides an easy on-machine inspection for caliper type brake linings. For all Off-Highway Truck models, it is important to replace the linings when they are worn to the wear indicator groove. Continued use of the linings past 3.15 mm (0.124 inch) of lining material or worn past the wear indicator groove depth will result in accelerated lining and disc wear.

• When measuring the lining, use a micrometer. Measure the inboard and outboard lining separately.

• Measure the linings at both ends because one end can wear more than the other.

• The lining resue criterion is summarized in Table 3. Table 4 provides a summary of the lining rebuild kits.

Illustration 7	g03697198
Lining reuse criteria (A) Thickness of the Lining.

Table 3

Lining Reuse Specifications Summary
Outboard Lining Part Number	Inboard Lining Part Number	As New Dimension (A)	Minimum Reuse Dimension (A)
114-9297	114-9299	24.7 mm (0.972 inch)	11.30 mm (0.445 inch)
8W-4939, 9C-0566	8W-4938, 9C-0567	27.5 mm (1.083 inch)	11.30 mm (0.445 inch)

Table 4

Lining Repair Kits
Outboard Lining Part Number	Inboard Lining Part Number	Repair Kit Part Number
114-9297	114-9299	114-9305
8W-4939, 9C-0566	8W-4938, 9C-0567	5T-2927, 6G-8619, 8W-4158 HD

Illustration 8	g03697226
Typical Example - Caliper Disc Brake (1) Linings (15) Disc

Brake Caliper Disc Wear

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NOTICE
Continued use of the disc beyond minimum thickness may result in loss of braking and possible catastrophic failure.

In general, normal disc life has three sets of linings (the original and two replacements). To ensure maximum disc life, it is important to follow the specifications in the “Lining Wear” section of this guide. Continued use of the linings past the Do Not Use Again specifications will result in accelerated disc wear. Inspect the disc (15) for damage and wear. Refer to Table 5 and replace the disc (15) if it does not meet the minimum reuse thickness.

Table 5

Caliper Disc Dimension Summary
As New Dimension	Minimum Reuse Specification
19.05 ± 0.5 mm (0.75 ± 0.020 inch)	15.87 mm (0.625 inch)

Brake Caliper Disc Grooves

Grooves in the disc faces are normal and do not affect lining life. Machining the face to remove the grooves is not necessary and will reduce the life of the disc.

Brake Caliper Disc Ridges

Improper brake usage can sometimes generate enough heat to cause the brake disc material to undergo plastic deformation, during at which time the surface material actually flows and piles up in front of the lining. If the ridges formed during the process are more than 0.3 mm (0.012 inch) high, Do Not Reuse the disc.

Illustration 9	g03697239
Brake disc material exhibiting the start of plastic deformation.

Illustration 10	g03697242
Ridges formed by plastic deformation are too high and act as cutting edges against the lining material.

Do Not Use Again

Illustration 11	g03697249
Ridges formed by plastic deformation are too high and act as cutting edges against the lining material. The brake disc is also showing signs of heat checking due to excessive heat generation.

Do Not Use Again

Multiple Disc Oil Cooled Type Brake

Illustration 12	g03697256
Disc and Plate Rear Service Brake - Typical Example (15) Brake Anchor (16) Brake Housing (17) Brake Hub (18) Brake Springs (19) Park Brake Piston (20) Service Brake Piston (21) Discs and Plates

Illustration 13	g03697277
Disc and Plate Front Service Brake - Typical Example (22) Parking/Secondary Piston (23) Service/Retarding Piston (24) Friction Discs (25) Plates (26) Brake Springs (27) Cooling Oil In (28) Cooling Oil Out

Multiple Disc Oil Cooled Brake Components - Wear Limits

The criteria for replacement of OHT brake discs, plates, and dampers at the time of an unscheduled repair or rebuild can vary. Each circumstance is unique, but inspection and replacement at these times can lower the number of repeat failures and improve rebuild component reliability of brake packs.

Disc Composition and Cleaning

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NOTICE
Do not use water, steam, water-based solutions, Freon, paint thinner, or ketones to clean discs.

Note: Be sure that you mark the original orientation of the brake discs in the pack before you remove the discs for inspection.

Illustration 14	g03697329
(31) Example of marked brake pack before disassembly and inspection.

The friction used on OHT brake discs is a Cellulose (paper) composition. Used disc color ranges from dark reddish brown 15 to dark gray or black 16

Illustration 15	g03697375
Cellulose brake disc. Note the reddish color.

Illustration 16	g03697385
Used cellulose brake disc. Note the gray/black disc color.

Note: Disc color alone cannot be used as a determination of disc reusability.

Disc color alone cannot be used as a “Reuse/Do Not Reuse” criterion. When cleaning a disc, do not allow the solvent to be absorbed into the disc. If solvent is allowed to absorb into the disc, seepage may contaminate the braking system after the disc is reinstalled. Also, some solvents might deteriorate the Cellulose composition.

Note: All friction discs can be cleaned with chlorinated solvents, diesel fuel, kerosene, and petroleum distillates using the following precautions.

• Solvent temperatures are less than 38° C (100° F).

• Rinse the discs with solvent or apply solvent with a siphoning blowgun. Use of a disc washer is also recommended. Refer to Illustration 24.

• Use towels or dry compressed air to dry the discs after washing.

• Hang the discs after drying. Do not stack.

Illustration 17	g03697390
Typical Example - Disc Washer

Disc Visual Inspection / Reusability Criteria

The discs shown in Illustrations 18 and 19 are reusable if the discs meet the minimum acceptable Percent Life Remaining thickness and groove depth dimensions.

Illustration 18	g03697392
Check minimum thickness and groove depth before reuse.

Illustration 19	g03697394
Check minimum thickness and groove depth before reuse.

Use Again

Handling Damage

Some brake disc damage may occur due to rough handling (contact with hard, sharp objects). The discs may be reused if they meet the following criteria.

• Discs are not usually “soft” or easily damaged during normal handling.

• A maximum of six damaged areas are permitted per face.

• The maximum allowable area of handling damage on any face is 100 mm² (0.16 inch²).

Cracks and Grooves

Any disc assembly that has a crack or deep grooves that stops a seal pick cannot be used again. Look for teeth that have been broken or cracked. Inspect the friction surfaces for radial cracks or deep grooves.

Bond Failure

Overheating of the friction faces, exposure to contaminated lube oil, or other incompatible materials can weaken the bond between the friction material and steel core. A weakened bond is indicated when material is easily and cleanly chipped off the core during normal handling.

Erosion

Disc erosion may result due to debris in the brake cooling oil and extended hours on the brake discs. In addition, cavitation erosion may occur of air is present in the brake cooling oil.

Disc erosion usually begins that the edges of the material, reducing the available friction surface and braking capability. Do Not Use Again if more than 10% of the disc surface is eroded.

Illustration 20	g03697404
(B) Eroded disc areas (C) Friction Material (D) New Disc Material (E) Steel Disc

Illustration 21	g03697407
Erosion is evident on the brake disc. Eroded area is less than 10% of the disc side.

Use Again

Illustration 22	g03697412
Eroded area is greater than 10% of disc surface.

Do Not Use Again

Illustration 23	g03697416
Disc erosion exceeds 10% of the disc surface.

Do Not Use Again

Water Damage

Exposure of the brake discs to water and antifreeze as a result of cooler core failure, vandalism, Improper cleaning, or accidental machine submersion will result in shortened service life. Discs damaged by water or other contaminants will experience material swelling and decay of the bonding adhesive. In addition, the friction material may easily come off during handling. Based on this, always replace the disc exposed to water or other contaminants.

Illustration 24	g03697429
Disc damaged by water contamination will experience material swelling and decay of bonding adhesive. Friction material may easily come off during handling.

Do Not Use Again

Illustration 25	g03697433
Disc damaged by water contamination. Notice the areas of flaking cellulose material. In addition, the charred lining bond adhesive on the teeth indicates water contamination.

Do Not Use Again

Illustration 26	g03697435
Do not use again because water contamination damage.

Do Not Use Again

The discs shown in Illustrations 24,25, and 26 have been damaged by contamination of the lubricating oil with water. Normal brake operation produces friction material temperatures above the boiling point of water, resulting in the rapid formation of steam in the lining.

The rapid, almost explosive formation of steam in the friction material causes the material to “flake off”. The material that remains on the disc is also weakened.

Another indicator of water contamination is the overall “charred” appearance of the bonding adhesive for the lining on the teeth.

Glazing

A surface becomes glazed from the heat generated during long periods of continuous braking or insufficient brake cooling. The heat hardens the friction material, leaving a shiny appearance. These material changes result in reduced braking capabilities. The reduced coefficient of friction resulting from the glazing causes additional slippage and finally complete brake failure. The material changes also reduce the adhesive bonding strength of the material and accelerate wear.

Glazing can be identified by a shiny appearance of the friction material. Glazing can cover the entire surface, or may be in bands. The normal surface has a porous appearance. Glazing is not permitted.

Illustration 27	g03697511
Glazed disc. Do not use again because disc is excessively glazed.

Do Not Use Again

Illustration 28	g03697518
Friction material is eroding in the area with the heaviest glazing.

Do Not Use Again

Overheating

High temperatures from insufficient oil cooling flow can over heat the friction material without glazing.

The disc shown in Illustration 29 has been overheated. The charring of the bonding adhesives for the lining on the teeth is typical of overheated discs. Discs worn to less than minimum groove depth become more likely to overheat. Overheating tends to accelerate wear and erosion (“flaking”) of the lining.

Illustration 29	g03697520
Do not use again because the disc is excessively over-heated and burnt.

Do Not Use Again

Disc Measurement

Illustration 30	g03697588
Measure disc thickness with a micrometer.

Illustration 31	g03697593
Measure the groove depth using a depth micrometer.

Illustration 32	g03697599
Disc Measurement Criteria (C) Lining (D) Steel Core

Disc Replacement Guidelines

1. Measure thickness and groove depth with micrometers to determine “Percent Life Remaining” for each disc. Refer to Table 6 or 7.

2. Measure lining wear on both sides of the disc

   Note: The lining wear should be even side-to-side. The lining in one side of the disc should not be less than 1/2 the thickness of the other side.

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   NOTICE
   Maximum of 20% difference in life remaining between discs reused in a brake pack.

3. Do Not Reuse a disc that has over 20% more wear than the other discs in a brake pack.

   Examples:

   • Do Not Reuse a disc that has 70% life remaining with a new disc that has 100% life remaining.

   • Do Not Reuse a combination of worn discs with 60%, 70%, and 90% life remaining.

4. Do Not Reuse a disc if more than 10% of the friction material has “flaked” off.

5. Do Not Reuse a disc if the friction material appears to be very easily chipped when using a light prying force with the tip of a knife.

   Note: The test presented in Step (5) must be applied with caution and within reason. If enough force is applied to the knife, even a new brake disc can be chipped. Do not use this as the only criteria to reject the use of a brake disc.

6. Do Not Reuse a disc if it has been damaged by contamination of water in the lubricating oil.

7. “Warped”, “glazed”, and/or “burnt” discs that exhibit signs of excessive temperature should be replaced in all instances. Refer to the “Disc Visual Inspection / Reusability Criteria” in this manual for additional information.

8. Inspect the disc teeth. Do not reuse discs with broken teeth. Do not reuse discs with a visible wear step in the disc teeth. Refer to the section “Tooth Wear Guideline” in this manual. Refer to Table 6 and 7 for minimum reuse dimensions.

Note: The reuse of worn brake discs, even those within specifications, can still cause the brake piston to stroke beyond the limits of the seals when reassembled in a brake pack. Extreme caution must be exercised when reusing brake discs.

Note: The reuse or replacement of only a selected number of worn or damaged brake discs may result in uneven wear and unequal brake cooling flow (heat dissipation) across the reused brake discs. Unequal brake cooling oil flow may occur between the disc and plate due to the different brake cooling groove depths found in reused brake discs. The increase in brake temperature across each individual brake disc can lead to brake disc glazing, resulting in higher loads to those brake discs that were replaced at the time of rebuild. This can cause premature failure and/or shorter overall component line.

Illustration 33	g03697600
Disc Dimension (A) Disc Thickness (B) Groove Depth

Table 6

Friction Disc Wear Table
Part Numbers: 5D-6329, 5D-7101, 7D-3014, 7T-7067, 7T-2629, 7T-2815, 8E-2183, 9W-7017, 9W-7018, 190-3532, 196-7866, 198-1137, 207-1266, 221-0775, 222-2333, 226-2826, 270-9292, 291-2901, 383-2734, 383-2735, 433-9478
Percent of Disc Wear	Disc Thickness (A) mm (in)	Minimum Groove Thickness (B) mm (in)
0	5.08 mm (0.200 inch)	0.64 mm (0.0252 inch)
10	5.03 mm (0.198 inch)	0.615 mm (0.0242 inch)
20	4.98 mm (0.196 inch)	0.590 mm (0.0232 inch)
30	4.93 mm (0.194 inch)	0.565 mm (0.0222 inch)
40	4.88 mm (0.192 inch)	0.540 mm (0.0213 inch)
50	4.83 mm (0.190 inch)	0.515 mm (0.0203 inch)
60	4.78 mm (0.188 inch)	0.490 mm (0.0193 inch)
70	4.72 mm (0.186 inch)	0.465 mm (0.0183 inch)
80	4.67 mm (0.184 inch)	0.440 mm (0.0173 inch)
90	4.63 mm (0.182 inch)	0.415 mm (0.0163 inch)
100	4.57 mm (0.180 inch)	0.390 mm (0.0154 inch)

Table 7

Friction Disc Wear Table
Part Numbers: 207-1265, 270-9293, 291-2902
Percent of Disc Wear	Disc Thickness (A) mm (in)	Minimum Groove Thickness (B) mm (in)
0	6.05 mm (0.238 inch)	1.05 mm (0.0413 inch)
10	6.00 mm (0.236 inch)	1.025 mm (0.0404 inch)
20	5.95 mm (0.234 inch)	1.000 mm (0.0400 inch)
30	5.90 mm (0.232 inch)	0.975 mm (0.0384 inch)
40	5.85 mm (0.230 inch)	0.950 mm (0.0374 inch)
50	5.80 mm (0.228 inch)	0.925 mm (0.0364 inch)
60	5.75 mm (0.226 inch)	0.900 mm (0.0354 inch)
70	5.70 mm (0.224 inch)	0.875 mm (0.0344 inch)
80	5.65 mm (0.222 inch)	0.850 mm (0.0335 inch)
90	5.60 mm (0.220 inch)	0.825 mm (0.0325 inch)
100	5.55 mm (0.218 inch)	0.800 mm (0.0315 inch)

Brake Dampers

All brake dampers should be replaced during a brake rebuild due to the shrinkage and deterioration of the damper material.

Tooth Wear Guideline

Disc assemblies should be inspected for tooth wear. Some tooth wear is acceptable, but never reuse a disc assembly that has obvious notches worn into the teeth.

Illustration 34	g03697602
Shows shallow wear but no obvious step. (A) Shallow wear but no obvious step. (B) Normal tooth surface.

Use Again

Illustration 35	g03697607
Shows notches worn into teeth. (B) Normal tooth surface. (C) Notch worn in tooth.

Do Not Use Again

Note: Be sure that you mark the original orientation of the brake discs in the pack before you remove them for inspection.

Illustration 36	g03697612
(30) Brake hub oil groove

When reassembling used discs, install discs in the same orientation as originally positioned. The disassembly and reassembly of worn discs orientated differently within the brake pack and running on the brake hub can result in brake disc tooth damage. Brake disc teeth located over the brake hub oil groove (30) will not wear the same as those located between the hub splines. Used brake discs should be installed with the unworn teeth in the brake hub oil groove location (30) to avoid teeth overloading and fracture. If the discs are not reinstalled in this orientation, the unworn disc teeth will experience increased loading from normal brake application and be prone to premature and catastrophic failure.

Plate Reusability Criteria

1. Do Not Reuse a plate if it's worn to less than the minimum Use Again thickness. Refer to Table 8 for a summary of the plate reuse dimensions.
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   Table 8

   Plate Thickness Dimension Summary
   Part Number	As New Dimension	Minimum Reuse Specifications
   7D-7504, 7D-7671, 9M-5588, 8W-0212, 8X-4437, 163-9366, 379-1822	2.413 ± 0.064 mm (0.0950 ± 0.0025 inch)	2.290 mm (0.090 inch)
   198-1203	2.704 ± 0.064 mm (0.10646 ± 0.00252 inch)	2.581 mm (0.10161 inch)
   145-5189	4.000 ± 0.08 mm (0.157 ± 0.003 inch)	3.877 mm (0.153 inch)

2. Do Not Reuse a plate if more than 10% of the surface area is scored. Refer to Illustration 37
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   Illustration 37	g03697616
   Do not use again because of excessive amount of scoring.

3. Do Not Reuse a plate if there are deep radial grooves that could cut the friction material. Refer to Illustration 39.
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   Illustration 38	g03697618

4. Do Not Reuse a plate that is warped. A plate is considered warped if it cannot be flattened by applying a 90 N (20 lb) force on the plate. See Illustration 39.

Illustration 39	g03697627
(D) 90 N (20 lb) weight (E) Plate (F) Flat top table (G) 0.038 mm (0.0015 inch) feeler gauge should fit between the plate and weight or table.

Multi Disc Brake Hub Reuse

Contact Area of the Hub Splines to the Wheel Hub Splines

Illustration 40	g03697632
(28) Contact area of the Hub splines to the wheel hub splines, fretting is possible in this area.

The brake hub may experience fretting wear on the splines attaching the brake hub to the wheel. Inspect the brake hub for fretting wear. Inspect the brake hub splines (28) to wheel hub splines for a wear step using a seal pick. When passing the seal pick over the wear step is stopped, there is more than 0.2 mm (0.008 inch) wear step. Typically, splines can be reused if less than 0.2 mm (0.008 inch) wear step exists.

Measure the brake hub splines as discussed in the section “Measurement Procedures” presented in the guidelines Reuse and Salvage Guideline, SEBF8225, "Reusability of Final Drive Splines Used on 785 - 797 Off Highway Trucks" and Reuse and Salvage Guideline, SEBF8759, "Reusability of Final Drive Splines Used on 769 - 784 Off Highway Trucks."

Contact Area of the Brake Disc to Hub Splines

The brake hub may experience fretting wear on the splines attaching the brake hub to the brake disc teeth. Inspect the brake hub for fretting wear.

Illustration 41	g03697636
Brake hub with fretting wear from the brake disc teeth.

Use Again

Inspect the brake disc tooth to the hub spline mating area for a wear step. Brake disc to the hub wear groove limit is 0.127 mm (0.005 inch) and should not stop a seal pick as it is crossed over the area.

Note: The wear step generated by the brake discs on the hub may hold the disc teeth during operation and result in a broken disc tooth. The broken disc teeth may then result in collateral damage to the brake pistons and the brake anchor.

Illustration 42	g03697639
(29) Brake disc to hub spline mating area

Brake disc to the hub wear groove limit is 0.127 mm (0.005 inch) and should not stop a seal pick as it is crossed over the worn area.

Illustration 43	g03697640
(32) The brake hub has a wear step in the spline that is approaching 0.127 mm (0.005 inch). Reuse of the brake hub must be carefully evaluated.

Illustration 44	g03697686
(33) The brake hub has a wear step on the spline that is more than 0.127 mm (0.005 inch). The wear step will cause the disc teeth to break.

Do Not Use Again

Service Brake Piston, Anchor, and Housing Reuse

Brake pistons, anchors, and housings have seal grooves and sealing surfaces which all have common reuse criteria.

Seal Groove Reusability

Seal groove integrity is essential to proper brake operation. Oil contamination, debris in the oil, and broken disc teeth can damage service brake seal grooves. Careful inspection of the seal grooves on all brake components is warranted. In order to reuse the component, a seal groove may be slightly deformed but must not be cracked or interfere with the seal movement.

Illustration 45	g03697689

This service piston has damage due to broken disc teeth. Note the close up view on the right that shows two broken disc teeth. The service piston damage is beyond repair in this example.

Do Not Use Again

Illustration 46	g03697697

(34) A broken disc tooth has resulted in this seal groove indentation. Seal grooves may be slightly deformed but must not be cracked or interfere with seal movement. A brake piston, anchor, or housing with a cracked seal groove or a seal groove that interferes with seal movement should not be used again.

Illustration 47	g03697700

(35) Seal ring groove with excessive deformation due to a broken disc tooth. Reuse of this service piston would result in improper seal function and potential catastrophic, premature service brake failure.

Do Not Use Again

Seal Contact Surface Reusability

Brake piston, anchor, and housing seal contact surfaces may show slight wear and polishing due to the mating seal traveling along the surface. The seal contact surface should not have wear or damage that can be detected with a seal pick. Wear that can be detected by a seal pick is excessive and can cause the seal to function improperly, which may result in loss of brake performance.

Illustration 48	g03697704

(36) OHT brake anchor seal contact surfaces.

Illustration 49	g03697706

(37) Brake piston seal surface.

Illustration 50	g03697709

(38) Service Technician buffing sealing surfaces.

Illustration 51	g03697711

Flapper wheel used to improve seal surface.

Minor wear and damage to sealing surfaces can be repaired and the part reused. Use a Grade F flapper wheel or a Scotch Brite Pad. Do not remove any of the parent material.

More extensive wear will require a component replacement or salvage. Metal Spray Technologies can be used to salvage service brake components. Refer to Reuse and Salvage Guidelines, SEBF9236, "Fundamentals of HVOF Spray for Reconditioning Components", Reuse and Salvage, SEBF9238, "Fundamentals of Arc Spray for Reconditioning Components" and Reuse and Salvage Guidelines, SEBF9240, "Fundamentals of Flame Spray for Reconditioning Components" for more information.