Types of 36 Rear Axle
The 36 rear axle, commonly referred to as the “Ford 9-inch axle,” is a legendary component in automotive history. First introduced by Ford in 1938, this axle was engineered for performance and reliability. Despite minimal changes over decades, it remains one of the most revered rear axles in the automotive world. Its robust design and adaptability have made it a go-to choice for hot rods, street rods, custom builds, and even modern muscle cars.
What sets the 36 rear axle apart is its modular design and compatibility with various configurations, allowing mechanics and enthusiasts to tailor it to different applications. Below are the primary types of 36 rear axles, each designed for specific needs and driving conditions:
Standard 36 Rear Axle
This is the original and most widely used version of the 36 rear axle. It features a cast iron housing that contains the ring and pinion gears responsible for transferring engine power to the wheels. Known for its rugged construction, the standard model is ideal for general use in classic vehicles and mild-performance builds.
Advantages
- Robust cast iron construction
- Widely available parts
- Cost-effective rebuild option
- Time-tested reliability
Limitations
- Heavier than modern alternatives
- Limited adjustability options
- Not ideal for extreme performance
Best for: Classic car restorations, daily drivers, light-duty performance builds
36 Rear Axle with Center Section
Also known as the “drop-out center section,” this configuration allows for easy removal of the differential assembly without dismantling the entire axle housing. This makes maintenance, gear changes, and repairs significantly faster and more convenient, especially for racers and tuners who frequently modify their setups.
Advantages
- Quick access to internal components
- Easier gear swaps and tuning
- Great for high-maintenance environments
- Preferred by performance tuners
Limitations
- Slightly higher cost
- May require alignment after reinstallation
- Less common in stock vehicles
Best for: Racing applications, frequent gear changes, workshop-friendly builds
36 Rear Axle with Floating Wheels
This variant includes a floating wheel design where the hubs are mounted externally on the axle housing. The wheels are attached using long bolts that pass through the hub and into the axle. This setup enhances load-bearing capacity and structural integrity, making it suitable for heavy-duty or high-torque applications.
Advantages
- Superior strength and stability
- Excellent for high-horsepower vehicles
- Better resistance to bending stress
- Popular in drag racing and trucks
Limitations
- More complex installation process
- Requires precise bolt torqueing
- Heavier than standard designs
Best for: Drag racing, off-road vehicles, high-torque engines
36 Rear Axle with Limited Slip Differential
This version integrates a limited slip differential (LSD), which improves traction by automatically distributing power between the two wheels when slippage occurs. Unlike open differentials, the LSD ensures both wheels receive torque, enhancing control during cornering and in low-traction situations.
Advantages
- Improved traction and handling
- Reduces wheel spin under load
- Enhances cornering performance
- Ideal for performance driving
Limitations
- Higher initial cost
- Requires periodic maintenance
- Can be noisy under certain conditions
Best for: Performance cars, track days, slippery road conditions
36 Rear Axle with Disc Brakes
This type replaces traditional drum brakes with disc brake systems, offering superior stopping power and heat dissipation. Disc brakes are less prone to fade under heavy braking, making them ideal for high-speed or high-performance vehicles. Upgrading to disc brakes can significantly enhance safety and braking efficiency.
Advantages
- Superior braking performance
- Better heat management
- Reduced brake fade
- Improved wet weather performance
Limitations
- More expensive upgrade
- Requires compatible calipers and rotors
- Additional clearance may be needed
Best for: High-performance builds, vintage cars needing modern upgrades, motorsport
36 Rear Axle with Adjustable Coilover Shocks
This advanced configuration includes coilover shocks mounted directly on the axle housing and vehicle chassis. These allow fine-tuning of ride height, suspension stiffness, and damping characteristics, giving drivers greater control over how their vehicle handles different driving conditions.
Advantages
- Customizable ride quality
- Enhanced handling and responsiveness
- Perfect for show and competition builds
- Easy adjustment for different terrains
Limitations
- Higher cost compared to standard shocks
- Requires suspension tuning knowledge
- Potential for harsh ride if not adjusted properly
Best for: Custom show cars, pro-touring builds, performance-oriented street machines
| Type | Main Feature | Strength | Best For | Maintenance Level |
|---|---|---|---|---|
| Standard 36 | Cast iron housing | High | Classic restorations, daily drivers | Low |
| Center Section | Removable differential | High | Racing, frequent tuning | Moderate |
| Floating Wheel | External hub mounting | Very High | Drag racing, heavy-duty use | Moderate |
| Limited Slip Diff | Traction-enhancing differential | High | Performance driving, corners | Moderate-High |
| Disc Brake Equipped | Modern braking system | High | Track use, upgraded safety | Moderate |
| Coilover Suspension | Adjustable ride settings | High | Custom builds, tuning | High |
Expert Tip: When building a custom vehicle with a 36 rear axle, consider matching your axle type to your intended usage—standard for cruiser builds, center section for track use, and floating wheels for maximum durability. Always ensure proper lubrication and regular inspection of bushings and bearings to maximize longevity.
Specifications and Maintenance of 36 Rear Axle
When selecting or servicing a 36 rear axle, understanding its specifications is crucial for ensuring compatibility, performance, and longevity. Below is a detailed breakdown of key components and their dimensional standards, followed by essential maintenance practices to keep your rear axle operating at peak efficiency.
Key Specifications to Consider
Before purchasing or repairing a 36 rear axle, it's important to verify the exact dimensions and design features that match your vehicle’s requirements. Each component plays a role in overall functionality, durability, and power transfer efficiency.
Axle Shaft
The axle shafts are critical driveline components responsible for transferring torque from the differential to the wheels. For the 36 rear axle:
- Length: Typically between 30–34 inches, depending on the vehicle model and wheelbase.
- Diameter: Ranges from 1.5 to 1.625 inches, providing strength while balancing weight considerations.
- Spline Count: Available with either 30 or 35 splines to accommodate different load capacities and driving conditions.
Selecting the correct spline count ensures proper engagement with the differential gears and prevents premature wear under high-torque applications.
Housings
The housing encases the differential and supports the axle shafts. It must be robust enough to withstand torsional forces and road impacts:
- Length: Measured between 57–60 inches from end to end.
- Width: Spans approximately 44–46 inches across the wheel mounting points.
- Diameter: The main housing tube diameter ranges from 8 to 10 inches for optimal structural integrity.
Proper housing alignment is vital for maintaining consistent gear mesh and preventing uneven wear on internal components.
Bearings
Bearings allow smooth rotation of the axle shafts within the housing. The standard bearing size for a 36 rear axle includes:
- Inner Diameter: 30 mm
- Outer Diameter: 62 mm
These bearings are typically tapered roller bearings designed to handle both radial and axial loads. High-quality bearings with sealed designs can significantly extend service intervals.
Gear Ratio
The gear ratio determines how many times the driveshaft rotates for each full turn of the wheels. The 36 rear axle offers ratios ranging from:
- Low Gear (3.73): Ideal for towing and low-speed torque applications.
- High Gear (5.13): Better suited for off-road crawling and maximum traction scenarios.
Choosing the right gear ratio depends on your driving style, terrain type, and engine characteristics.
Pinion Size
The pinion gear meshes with the ring gear to transmit power from the driveshaft to the differential. On the 36 rear axle:
- Size: Pinion diameter measures between 8–9 inches.
- Teeth Count: Features 9–11 teeth depending on the gear ratio selected.
Precision machining and proper tooth contact pattern are essential for minimizing noise and maximizing lifespan.
Ring Gear Size
The ring gear is bolted to the differential carrier and works in tandem with the pinion gear:
- Diameter: Ranges from 10–11 inches.
- Teeth Count: Contains up to 40–42 teeth, matching the pinion’s tooth profile for optimal meshing.
Mismatched or worn ring and pinion gears can lead to vibration, noise, and loss of power transfer efficiency.
| Component | Measurement Range | Notes |
|---|---|---|
| Axle Shaft Length | 30–34 inches | Varies based on vehicle application |
| Axle Shaft Diameter | 1.5–1.625 inches | Impacts strength and fitment |
| Spline Count | 30 or 35 | Higher count for higher torque capacity |
| Housing Length | 57–60 inches | Ensures proper wheelbase alignment |
| Housing Width | 44–46 inches | Determines track width |
| Housing Diameter | 8–10 inches | Thicker tubes increase rigidity |
| Bearing Dimensions | 30 mm (ID), 62 mm (OD) | Standard tapered roller bearings |
| Gear Ratio | 3.73–5.13 | Choose based on use case (towing/off-road) |
Essential Maintenance Practices
To ensure long-term reliability and performance of your 36 rear axle, regular inspection and preventive maintenance are essential. Here are some best practices to follow:
Important: If you're replacing any part of the 36 rear axle system, consider evaluating and replacing all related components together. Mismatched or unevenly worn parts can create imbalance, reduce performance, and shorten the life of new components.
How to Choose a 36 Rear Axle
Selecting the right 36 rear axle is crucial for ensuring vehicle performance, safety, and longevity. Wholesale buyers must consider various technical and practical factors to meet diverse customer needs across different applications.
Identify the Purpose and Application
The primary consideration when selecting a 36 rear axle is understanding its intended use. Whether it’s destined for heavy-duty commercial trucks, rugged off-road vehicles, or high-performance sports cars, each application demands specific design characteristics.
- Heavy-duty trucks: Require robust construction with high load-bearing capacity and heat resistance
- Off-road vehicles: Benefit from reinforced housings and oil seals that withstand dirt and moisture
- Performance cars: Need lightweight designs with optimized gear ratios for acceleration and handling
Critical check: Always verify manufacturer specifications against expected usage conditions
Understand Axle Terminology
Familiarity with key axle terminology helps buyers make informed decisions and communicate effectively with customers about product features and benefits.
- Gear ratio: The number of driveshaft rotations per wheel revolution (e.g., 3.73:1 means 3.73 driveshaft turns per wheel rotation)
- Splines: The teeth on axle shafts that connect to differential gears or wheel hubs – more splines generally mean greater strength
- Axle rating: Refers to the maximum weight capacity the axle can safely handle under normal operating conditions
Technical note: Most 36 rear axles feature either 30 or 33 spline configurations
Consider Gear Ratio Selection
The gear ratio significantly impacts vehicle performance characteristics, affecting acceleration, fuel efficiency, towing capability, and highway cruising comfort.
- Lower ratios (e.g., 3.31:1): Provide more torque multiplication for heavy towing and off-road performance
- Moderate ratios (e.g., 3.73:1): Offer balanced performance for mixed driving conditions
- Higher ratios (e.g., 4.10:1): Improve acceleration but may reduce highway fuel economy due to higher RPM at cruising speeds
Optimization tip: Consider tire size changes when evaluating gear ratio requirements
Axle Strength and Durability Features
Proper evaluation of axle construction materials and manufacturing processes ensures long-term reliability and customer satisfaction.
- Material quality: Look for forged steel components with proper heat treatment for optimal hardness and toughness
- Bearing design: Sealed bearings offer better protection against contaminants compared to traditional serviceable units
- Oil sealing systems: Multi-lip seals provide superior protection against lubricant loss and contaminant ingress
- Surface treatments: Powder coating or zinc plating enhances corrosion resistance in harsh environments
Quality indicator: Reputable manufacturers often publish SAE certification standards for their components
Buying Recommendation: When uncertain about customer requirements, recommend axles with standard gear ratios and mid-range strength ratings as versatile options. These typically satisfy most common applications while allowing for future upgrades if needed. Always prioritize OEM compatibility specifications over generic replacements.
| Application Type | Recommended Gear Ratio | Minimum Spline Count | Material Specification |
|---|---|---|---|
| Light truck/SUV daily driver | 3.54-3.73 | 30 spline | Grade 1045 steel |
| Medium/heavy towing | 3.73-4.10 | 33 spline | Forged alloy steel |
| Off-road recreation | 4.10-4.56 | 33 spline | Heat-treated chromoly |
| Racing/performance | Custom matched | 35+ spline | Aerospace-grade alloys |
Brake System Compatibility
Ensuring proper brake system integration is essential for safe operation and regulatory compliance. This includes physical mounting dimensions and performance capabilities.
- Verify brake rotor/hub interface dimensions match existing suspension components
- Check caliper mounting bracket compatibility with selected axle housing
- Confirm ABS sensor provisions if required by vehicle configuration
- Ensure adequate clearance for brake lines and parking brake mechanisms
Safety reminder: Improper brake compatibility can lead to reduced stopping power and premature component wear
Suspension Integration Requirements
The rear axle must work harmoniously with the vehicle's suspension system to maintain proper geometry, articulation, and ride characteristics.
- Match spring perch locations to existing suspension setup
- Verify shock mount positioning for optimal damping performance
- Check pinion angle compatibility with drivetrain configuration
- Ensure adequate ground clearance for intended usage
Installation note: Some modified suspensions may require custom axle housing fabrication
Supplier Evaluation: Prioritize suppliers who offer comprehensive documentation including installation guides, torque specifications, and maintenance recommendations. Extended warranties and technical support services indicate confidence in product quality and reliability.
Comprehensive DIY Guide for Replacing a 36 Rear Axle
Replacing a rear axle is a significant mechanical task that, when approached with the right preparation and tools, can be accomplished successfully by experienced DIYers. This guide provides detailed instructions to help you replace your 36 rear axle efficiently and safely.
Safety Warning: Working on vehicle axles involves heavy components, lifting equipment, and potential fluid hazards. Always wear safety glasses, gloves, and ensure your vehicle is securely supported before beginning any work.
Tools and Materials Required
- New 36 rear axle assembly (ensure it's compatible with your vehicle make and model)
- Hydraulic jack and sturdy jack stands
- Complete socket set (standard and metric sizes)
- Adjustable wrench and open-end wrenches
- Digital or beam-style torque wrench
- Ball-peen hammer and pry bar
- Safety glasses and mechanic’s gloves
- Drain pan for collecting old gear oil
- Recommended gear oil for refilling
- Brake cleaner and degreaser
Step-by-Step Replacement Process
- Prepare the Vehicle
- Park the vehicle on a flat, level surface and engage the parking brake.
- Turn off the engine and allow it to cool if recently driven.
- Disconnect the negative terminal of the battery for added electrical safety.
- Take reference photos of the existing axle setup to aid reassembly later.
- Lift the Vehicle Safely
- Locate the manufacturer-recommended lift points under the vehicle frame.
- Raise the rear of the vehicle using a hydraulic jack until both rear wheels are off the ground.
- Secure the vehicle on jack stands placed under reinforced support points.
- Double-check stability before working underneath the vehicle.
- Remove the Wheels
- Loosen the wheel lug nuts while the vehicle is still on the ground.
- Once lifted, completely remove the lug nuts and take off both rear wheels.
- Store the lug nuts in a safe place to avoid losing them during the process.
- Drain the Axle Fluid
- Place a drain pan beneath the rear axle housing to collect the gear oil.
- Remove the fill plug first to allow air flow, then remove the drain plug.
- Allow all the old fluid to drain completely before replacing the drain plug.
- Dispose of used gear oil responsibly at an approved recycling center.
- Disconnect Suspension Components
- Identify and label suspension components connected to the rear axle—this may include leaf springs, trailing arms, control arms, or sway bars.
- Use appropriate sockets or wrenches to loosen and remove bolts securing these components.
- Support disconnected components temporarily to prevent strain on other parts.
- Detach the Driveshaft
- Mark the position of the driveshaft relative to the pinion yoke for proper alignment upon reinstallation.
- Remove bolts connecting the driveshaft to the differential flange.
- Carefully slide the driveshaft forward and lower it from the vehicle.
- Set it aside in a clean area where it won’t get damaged.
- Disconnect the Brake System
- Unbolt the caliper brackets and hang the calipers securely out of the way using wire or bungee cords.
- Plug the open ends of the brake lines to prevent fluid leakage and contamination.
- Remove the rotor if necessary, and keep all hardware together for easy reassembly.
- Remove the Differential Cover
- Remove the bolts securing the differential cover plate.
- Gently tap around the edges with a rubber mallet to break the seal.
- Inspect the internal gears and bearings for excessive wear while you have access.
- Remove the Old Rear Axle
- Ensure all connections (electrical, mechanical, and hydraulic) have been disconnected.
- Use a transmission jack or sturdy floor jack to support the rear axle assembly.
- Remove mounting bolts that secure the axle to the vehicle chassis or frame.
- Slowly lower the axle and carefully maneuver it out from beneath the vehicle.
- Install the New Rear Axle Assembly
- Position the new 36 rear axle into place using the jack for support.
- Align the axle properly with the vehicle’s mounting points and frame rails.
- Install and hand-tighten all mounting bolts before final tightening.
- Torque all bolts to the manufacturer’s specifications using a calibrated torque wrench.
- Reinstall the Differential and Components
- If applicable, reinstall the differential unit onto the new axle housing.
- Replace the differential cover with a new gasket and torque bolts evenly.
- Reconnect the driveshaft using the original markings for proper alignment.
- Reconnect the Brake Lines and Components
- Reattach the brake calipers and rotors to their original positions.
- Reconnect the brake lines carefully, ensuring no leaks or kinks.
- Bleed the brake system thoroughly after completing the installation.
- Refill Axle Fluid
- Remove the fill plug and pour in the recommended type and amount of gear oil.
- Fill until the oil reaches the bottom of the fill hole, then reinstall the plug securely.
- Check for leaks once the fluid has settled for a few minutes.
- Lower the Vehicle and Final Checks
- Verify all tools and materials have been removed from under the vehicle.
- Gradually lower the vehicle off the jack stands using the hydraulic jack.
- Reinstall the rear wheels and torque the lug nuts to specification.
- Start the engine and check for unusual noises, vibrations, or fluid leaks.
| Phase | Key Actions | Common Pitfalls | Essential Tools |
|---|---|---|---|
| Preparation | Vehicle positioning, tool gathering, component labeling | Mismatched axle size, insufficient workspace | Jacks, camera, marking tape |
| Disassembly | Removing wheels, draining fluid, disconnecting components | Fluid spills, missing bolt labels | Socket set, drain pan, wrenches |
| Axle Removal | Proper lifting, bolt removal, axle extraction | Inadequate support, dropped components | Floor jack, transmission jack, pry bar |
| Installation | Alignment, bolt tightening, torque specs | Improper torque, misalignment | Torque wrench, alignment tools |
| Reassembly | Reconnecting systems, fluid refill, testing | Leaking seals, missed connections | Fluids, pressure tester, bleed kit |
DIY Tip: Before installing the new axle, inspect and replace any worn bushings or mounts. Also, consider upgrading to synthetic gear oil for better performance and longevity if your vehicle will see high-stress conditions.
Post-Replacement Testing and Break-In
- Perform a thorough visual inspection of all connections and fasteners.
- Take a short test drive at low speed to monitor for abnormal noises or vibrations.
- Recheck all fluid levels after driving a short distance.
- Follow the manufacturer’s recommended break-in procedure for optimal axle performance.
Rear Axle FAQ: Understanding Sizes and Benefits
The 36 rear axle is the most commonly used size across a wide range of vehicles, especially in light to medium-duty applications. While other sizes such as 44 and 30 rear axles exist — often serving more specialized or lightweight purposes — the 36 rear axle strikes an optimal balance between strength, durability, and compatibility with various vehicle types. This makes it the go-to choice for many manufacturers and aftermarket builders alike.
The primary differences between a 28 and a 36 rear axle lie in their gear dimensions, overall structural integrity, and intended usage. The 36 rear axle features larger ring and pinion gears compared to the 28, which translates into greater torque handling capacity and improved reliability under load. Additionally, the housing of a 36 rear axle is typically sturdier, making it suitable for vehicles that require enhanced performance and longevity, especially when towing or navigating rough terrain.
The 36 rear axle offers several key advantages that make it a preferred option among mechanics and vehicle enthusiasts:
- Increased Strength: Its robust design allows for better handling of high-torque applications and off-road demands.
- Larger Tire Compatibility: The 36 rear axle supports wider and taller tires, which can enhance traction and ground clearance — particularly beneficial for trucks and SUVs.
- Improved Fuel Efficiency: Due to its optimized gear ratios and reduced drivetrain stress, the 36 rear axle can contribute to slightly better fuel economy compared to heavier or less efficient axle designs.
- Aftermarket Support: Because of its popularity, there’s a wide array of performance parts and upgrades available for the 36 rear axle, from gear kits to lockers and stronger differentials.
These benefits make the 36 rear axle a versatile and reliable choice for both daily drivers and performance-focused builds.