At XZAPART, we manufacture precision axle components for heavy-duty commercial vehicles, including axle housings, differential cases, reducer parts, and custom-machined assemblies.For customers who purchase or design axle-related components, understanding how each part functions inside the axle system is crucial for selecting the right solution and ensuring long-term vehicle reliability.

This article provides a clear, engineer-level explanation of the major components used in drive axles, steering axles, and supporting axles, based on our 20+ years of OEM manufacturing experience.

1. Drive Axle: Core Structure & Functional Parts

The drive axle is the most complex assembly in a heavy-duty truck.Its job is to receive power, reduce speed, increase torque, and deliver that torque to the wheels, while simultaneously carrying the full vehicle load.

Below are the main components used in a standard single-reduction drive axle.

1. Axle Housing

The axle housing is the foundation of the entire axle assembly.

Functions:

• Structural body that supports the final drive, differential, axle shafts, and wheel ends

• Bears vertical load, lateral forces, driving torque, and braking torque

• Contains gear oil used to lubricate and cool the differential gears

• Available in banjo-type (integral) and sectional designs

As an axle housing manufacturer, XZAPART supplies high-strength, CNC-machined housings designed for heavy loads and long service life.

2. Final Drive (Main Reduction Gear)

This is the heart of the torque-multiplying system.

Functions:

• Reduces speed and increases torque using a pinion and ring gear

• Changes the direction of power from longitudinal (driveshaft) to lateral (wheels)

• Determines the axle ratio, which influences fuel economy, climbing ability, and acceleration

XZAPART provides precision-machined reducer housings and gear-related components for high-load applications.

3. Differential Assembly

The differential ensures smooth power delivery while allowing different wheel speeds.

Functions:

• Allows the left and right wheels to rotate at different speeds during turning

• Splits torque evenly between both half shafts

• Includes differential casing, planetary gears, side gears, and spider gear set

Our differential housings and related components are produced with strict machining tolerances to ensure durability and smooth gear engagement.

4. Hub Reduction (for Hub-Reduction Axles)

Used in mining trucks, off-road vehicles, and applications requiring extra torque.

Functions:

• Provides secondary reduction at the wheel end

• Increases wheel-end torque while reducing load on the center gearbox

• Improves ground clearance by allowing a smaller central housing

Components include sun gears, planet gears, ring gears, and carriers—parts XZAPART can customize for OEM and aftermarket needs.

5. Axle Shafts

These deliver power directly from the differential to the wheels.

Functions:

• Transmit torque under high load

• Heavy-duty trucks use full-floating axle shafts, which only handle torque—not vertical load—ensuring higher safety

XZAPART produces precision-forged and CNC-machined axle shaft components for consistent performance.

6. Wheel-End Assembly

A critical load-bearing and rotational unit.

Functions:

• Supports the vehicle weight via hub and bearings

• Allows smooth wheel rotation

• Serves as the mounting base for brake drums or discs

• Includes seals to prevent mud, water, and grease leakage

Many modern heavy trucks use maintenance-free hub units, which XZAPART also supplies depending on customer requirements.

7. Brake Components Integrated with the Axle

These parts convert pneumatic or hydraulic force into braking torque.

Key components:

• Brake drum or brake disc

• Brake shoes or calipers

• Brake chamber

• Automatic slack adjuster

These braking parts must be precisely aligned with the axle housing and wheel end for maximum safety.

2. Steering Axle Components

A steering axle performs three main tasks: load-bearing, steering, and braking support.

Main components include:

• Axle Beam (I-beam) — forged or machined to withstand complex loads

• Steering Knuckles — rotate around the kingpin to provide steering movement

• Wheel-End Assembly — similar to the drive axle but without power transmission

• Brake System — typically disc or drum brakes

• Steering Linkages — tie rods transferring steering gear motion

XZAPART supplies knuckles, axle beams, and wheel-end components for various heavy-duty truck brands.

3. Supporting Axle (Tag / Lift Axle)

A supporting axle helps distribute weight and improve vehicle stability.Most do not provide power or steering, though some can be pneumatically lifted.

Components:

• Axle beam

• Wheel-end assemblies

• Brake system

• Air-lift or mechanical lift mechanism

These axles reduce ground pressure and extend tire life under partial-load conditions.

4. How the Axle System Works (Simplified Flow)

Power Transmission Path

Engine → Transmission → Driveshaft → Pinion → Ring Gear → Differential → Half Shafts → Hub Reduction (if applicable) → Wheel

Load & Braking

Vehicle load → Suspension → Axle Housing → Wheel Bearings → WheelsBraking force → Drum/Disc → Wheel → Axle → Chassis

Conclusion

Heavy-duty truck axles are highly engineered systems designed to endure extreme loads, long distances, and harsh road conditions.At XZAPART, we focus on delivering precision-machined axle components that enhance:

• Power transmission efficiency

• Load-bearing stability

• Braking safety

• Service life and reliability

With decades of OEM experience and advanced machining capabilities, we support global customers in commercial vehicle manufacturing, aftermarket service, and custom axle component production.