Wheel Bearing Maintenance - GM Square Body Trucks (1973-1987)

Overview

Wheel bearing maintenance is a critical aspect of Square Body truck ownership that directly affects safety, handling, and tire wear. These trucks utilize tapered roller bearings in both front and rear applications, with different configurations depending on drive type and axle specifications. Proper maintenance involves regular inspection, cleaning, repacking with grease, and replacement when necessary.

Square Body trucks are known for their robust bearing systems, but after 35+ years, most original bearings require attention. The front wheel bearings on 2WD models are serviceable without removing the hub, while 4WD models require more extensive disassembly. Rear wheel bearings vary significantly between full-floating and semi-floating axle configurations.

Why This Matters:
- Prevents catastrophic wheel separation
- Eliminates wheel wobble and vibration
- Extends tire life through proper wheel alignment
- Maintains steering precision and road feel
- Prevents costly damage to spindles, hubs, and axle housings

Common Issues

Front Wheel Bearings

• Excessive play - Most common issue, causing wheel wobble and uneven tire wear
• Noise during turns - Growling or rumbling that changes with steering input
• Heat buildup - Over-tightened or under-greased bearings generate excessive heat
• Grease contamination - Water intrusion through worn seals causes bearing failure
• Improper adjustment - Too loose causes play, too tight causes premature failure

Rear Wheel Bearings

• Axle seal leakage - Gear oil contamination destroys bearing grease
• Bearing race spinning - Common in semi-floating axles, requires housing repair
• C-clip failure - 10-bolt axles can lose C-clips, causing axle shaft movement
• Hub bearing failure - Full-floating axles develop play in hub bearings

Universal Issues

• Corrosion - Salt exposure causes pitting and premature failure
• Overloading - Exceeding GVWR accelerates bearing wear
• Neglected maintenance - Bearings not serviced in decades

Parts & Materials Needed

Front Wheel Bearings (2WD)

Inner Bearing Sets:

Timken LM67048/LM67010 (Standard)
National A-6 (Alternative)
SKF BR6 (Premium)

Outer Bearing Sets:

Timken L68149/L68111 (Standard)
National A-5 (Alternative) 
SKF BR5 (Premium)

Seals:

National 8734S (Standard)
Timken 8734S (OEM Equivalent)

Front Wheel Bearings (4WD)

1973-1980 K-Series:

Inner: Timken LM67048/LM67010
Outer: Timken L68149/L68111
Seal: National 8734S

1981-1987 K-Series:

Inner: Timken 15123/15245
Outer: Timken L68149/L68111  
Seal: National 710307

Rear Wheel Bearings

10-Bolt Semi-Floating (7.5" & 8.5"):

Timken 1580/1520 (Standard application)
National A-23 (Alternative)

12-Bolt Semi-Floating (8.875"):

Timken 28680/28622
National A-31

Full-Floating (14-Bolt & Dana 60):

Hub Bearings: Timken HM88648/HM88610
Lock Nuts: GM Part #14077352

Tools Required

Essential Tools:
- Bearing race driver set
- Bearing puller set
- Torque wrench (0-150 ft-lbs)
- Inch-pound torque wrench (0-200 in-lbs)
- Dial indicator with magnetic base
- Bearing packer tool or grease gun

Specialized Tools:
- Hub puller (4WD applications)
- Slide hammer with bearing puller attachments
- Race installation tools (specific to bearing size)
- Axle puller (semi-floating rear axles)

Materials

Grease:
- Mobil 1 Synthetic Grease (Premium choice)
- Lucas Red 'N' Tacky (High-temp performance)
- Valvoline Multi-Purpose (Budget option)
- Quantity: 1 tube per axle end

Cleaning Supplies:
- Brake cleaner or degreaser
- Shop rags
- Wire brushes
- Parts washing solvent

Step-by-Step Guide

Front Wheel Bearings (2WD Models)

Removal and Inspection

1. Safety Preparation
   - Jack up vehicle and secure with jack stands
   - Remove wheel and tire assembly
   - Remove brake caliper and suspend with wire (do not let hang by brake line)

2. Disassembly
   Remove dust cap (pry carefully to avoid damage) Remove cotter pin from castle nut Remove castle nut and flat washer Remove outer bearing by hand Pull rotor/hub assembly straight off spindle

3. Inner Bearing Removal
   - Remove grease seal from back of hub (discard)
   - Remove inner bearing from hub
   - Clean all components with brake cleaner

4. Race Inspection and Removal
   - Inspect bearing races in hub for pitting, scoring, or wear
   - Remove races using bearing race driver and hammer
   - Critical: Always replace races when replacing bearings

Installation

1. Race Installation
   Install outer race: Drive in squarely using race driver Install inner race: Ensure full seating against hub shoulder Verify races are fully seated with feeler gauge

2. Bearing Preparation
   - Pack bearings with high-quality wheel bearing grease
   - Work grease completely through bearing rollers
   - Apply thin layer of grease to spindle

3. Assembly
   Install inner bearing in hub Install new grease seal (coat outer edge with sealer) Slide hub assembly onto spindle Install outer bearing Install flat washer and castle nut

4. Adjustment Procedure
   Step 1: Tighten castle nut to 12 ft-lbs while rotating hub Step 2: Back off nut completely (2-3 full turns) Step 3: Hand tighten nut until snug Step 4: Back off 1/6 to 1/4 turn until loose Step 5: Install cotter pin through nearest hole

5. Final Check
   - End play should be 0.001" to 0.005"
   - Hub should rotate freely without binding
   - No perceptible play when checking by hand

Front Wheel Bearings (4WD Models)

Additional Considerations for 4WD

1. Hub Removal
   - Remove locking hubs (manual) or hub caps (automatic)
   - Remove snap ring and axle shaft
   - Hub assembly requires puller for removal

2. Bearing Differences
   - 1981-1987 models use different inner bearing size
   - Some applications use unitized hub assemblies
   - CV joint interference may require special tools

Rear Wheel Bearings (Semi-Floating)

10-Bolt and 12-Bolt Axles

1. Axle Removal
   Remove differential cover and drain gear oil Remove differential pinion shaft lock bolt Remove pinion shaft Push axle shaft inward and remove C-clip Pull axle shaft from housing

2. Bearing Removal
   - Use slide hammer with bearing puller attachment
   - Remove old seal (always replace)
   - Clean bearing bore thoroughly

3. Installation
   Install new bearing using bearing driver Install new seal with sealer on outer edge Reinstall axle shaft and C-clip Reassemble differential components

Rear Wheel Bearings (Full-Floating)

14-Bolt and Dana 60 Axles

1. Hub Disassembly
   Remove axle shaft (8 bolts) Remove outer lock nut (left-hand thread on right side) Remove lock washer Remove inner adjusting nut Pull hub assembly straight out

2. Bearing Service
   - Remove outer bearing from hub
   - Drive out inner seal and remove inner bearing
   - Clean and inspect all components
   - Replace races if bearings are replaced

3. Assembly and Adjustment
   Install inner bearing and new seal Install hub on axle tube Install outer bearing Install inner nut and tighten to 65 ft-lbs while rotating hub Back off 1/4 turn, then hand tighten Install lock washer and outer nut Torque outer nut to 65 ft-lbs

Year/Model Differences

1973-1980 vs 1981-1987

Front Bearings:
- 1973-1980: Consistent bearing sizes across all models
- 1981-1987: 4WD models received larger inner bearings (LM67048 to 15123)
- Seal Changes: 1981+ models use different seal part numbers

Rear Axle Variations:
- 1973-1980: Primarily 10-bolt and 12-bolt semi-floating
- 1981-1987: Introduction of 14-bolt full-floating in heavy-duty applications

Model-Specific Differences

C10/C20 (2WD):
- Simpler front bearing service (no hub removal required)
- C20 models may have upgraded bearing sizes for higher load capacity

K10/K20 (4WD):
- More complex front bearing service due to hub design
- K20 models typically use same bearings as K10 (capacity handled by axle design)

K5 Blazer:
- Same as K10 truck through 1980
- 1981-1987 models follow updated 4WD bearing specifications

Suburban:
- Generally follows truck specifications based on series (10 vs 20)
- Some heavy-duty packages may use upgraded components

Axle Code Identification

Common Rear Axle Codes:

Code G (7.5" 10-bolt): Standard C10, light-duty K10
Code H (8.5" 10-bolt): Heavy-duty C10, standard C20  
Code K (8.875" 12-bolt): Performance applications
Code F (9.5" 14-bolt): Heavy-duty C20, K20 applications

Tips & Best Practices

Maintenance Schedule

Inspection Intervals:
- Every 30,000 miles: Check for play and noise
- Every 60,000 miles: Repack front bearings (2WD)
- Every 100,000 miles: Replace bearings preventively

Professional Techniques

Bearing Installation:
- Always replace races when replacing bearings
- Use proper bearing drivers to prevent damage
- Never mix old and new components
- Heat races slightly (200°F) for easier installation

Grease Selection:
- Synthetic grease for extreme temperatures
- High-temp grease for heavy towing applications
- Standard lithium for normal use
- Apply grease to spindle threads to prevent corrosion

Torque Specifications:

Front wheel bearing adjustment: Hand tight minus 1/6 turn
Full-floating rear hubs: 65 ft-lbs initial, back off 1/4 turn
Brake caliper mounting: 35 ft-lbs
Lug nuts: 90 ft-lbs (steel wheels), 100 ft-lbs (aluminum)

Common Mistakes to Avoid

• Over-tightening front wheel bearings (causes premature failure)
• Reusing old grease seals (leads to contamination)
• Mixing bearing brands (different tolerances cause issues)
• Improper race installation (cocked races fail quickly)
• Contaminated grease (water/dirt intrusion destroys bearings)

Cost-Saving Tips

Budget Approaches:
- Repack existing bearings if in good condition
- Use quality aftermarket bearings (Timken, National, SKF)
- Buy bearing sets rather than individual components

When to Upgrade:
- High-mileage vehicles: Always replace races with bearings
- Heavy-duty use: Consider premium synthetic grease
- Restoration projects: Replace all seals and hardware

Troubleshooting

Diagnostic Procedures

Wheel Play Check:
1. Jack up vehicle and secure with jack stands
2. Grasp tire at 12 and 6 o'clock positions
3. Rock tire back and forth
4. Excessive play indicates: Worn bearings or improper adjustment

Noise Diagnosis:
- Rumbling during straight driving: Usually rear bearings
- Noise changes with steering: Front bearing on opposite side of turn
- Clicking during turns: CV joints (4WD) or worn bearings
- Grinding noise: Severely worn bearings (immediate attention required)

Specific Problem Solutions

Problem: Wheel wobble at highway speeds

Likely Causes:
- Loose front wheel bearings
- Worn bearing races  
- Improper bearing adjustment
- Bent spindle or hub

Solution:
- Check bearing adjustment first
- Inspect races for wear or damage
- Verify proper torque on all components
- Check hub runout with dial indicator

Problem: Premature bearing failure

Likely Causes:
- Over-tightened adjustment
- Contaminated grease
- Improper installation
- Overloading vehicle

Solution:
- Follow proper adjustment procedure
- Use clean, appropriate grease
- Verify race installation is square
- Check vehicle loading practices

Problem: Grease leakage

Likely Causes:
- Worn or damaged seals
- Over-greasing
- Improper seal installation
- Damaged spindle or hub

Solution:
- Replace seals with proper sealant
- Use appropriate grease quantity
- Verify seal orientation and seating
- Inspect mating surfaces for damage

Emergency Repairs

Roadside Bearing Failure:
- Immediate action: Stop driving immediately
- Temporary fix: Not recommended for bearings
- Professional help: Required for safe repair
- Towing: Necessary to prevent further damage

Warning Signs Requiring Immediate Attention:
- Metal-on-metal grinding sounds
- Wheel feels loose when jacked up
- Excessive heat from wheel area
- Visible grease leakage with metal particles

Parts Availability and Sources

OEM Quality Sources:
- Timken: Premium bearing manufacturer
- National/Federal Mogul: OEM supplier quality
- SKF: European premium alternative

Aftermarket Sources:
- LMC Truck: Complete bearing kits with instructions
- Classic Parts of America: OEM-style components
- Brothers Truck Parts: Competitive pricing on quality parts

Local Availability:
- Most auto parts stores stock common Square Body bearings
- NAPA and Carquest typically have best coverage
- Dealer parts still available for some applications