INDUSTRY COMPONENT

Side Gears (Sun Gears)

Side gears, also known as sun gears, are critical components in automotive rear differentials that transfer torque to the drive axles while allowing speed differentiation during turns.

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Component Specifications

Definition
Side gears (sun gears) are bevel gears positioned within the differential case of a rear differential assembly. They mesh with the spider gears (pinion gears) to distribute torque from the ring gear to the drive axles. These gears enable the left and right wheels to rotate at different speeds during cornering, preventing wheel slippage and ensuring smooth vehicle handling. They are essential for power transmission in rear-wheel-drive and all-wheel-drive vehicles.
Working Principle
Side gears operate on the principle of differential gearing. They receive rotational input from the ring gear via the differential case and spider gears. During straight-line driving, both side gears rotate at the same speed, transferring equal torque to the axles. During turns, the spider gears rotate around the side gears, allowing one side gear to rotate faster than the other, accommodating the different path lengths of the wheels.
Materials
Typically forged or machined from high-strength alloy steels such as SAE 8620, SAE 8822, or SAE 4320, often case-hardened via carburizing or nitriding to achieve surface hardness of 58-62 HRC and a tough core. Some applications use powder metallurgy steels for cost efficiency.
Technical Parameters
  • Backlash 0.10-0.20 mm
  • Tooth Type Straight or spiral bevel
  • Module/Pitch 2.5-5 mm (varies by vehicle load)
  • Core Hardness 28-35 HRC
  • Pressure Angle 20-22 degrees
  • Number of Teeth 10-16 (design-dependent)
  • Runout Tolerance <0.05 mm
  • Surface Hardness 58-62 HRC
Standards
ISO 1328-1, DIN 3961, AGMA 2008-B01, SAE J1545

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Side Gears (Sun Gears).

side gears sun gears rear differential gears automotive differential components bevel gears torque transmission differential assembly axle gears vehicle powertrain Side Gears (Sun Gears) Side Gears (Sun Gears) in Motor Vehicle Manufacturing

Parent Products

This component is used in the following industrial products

Rear Differential

A mechanical device in the drivetrain that splits torque between the rear wheels while allowing them to rotate at different speeds.

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Engineering Analysis

Risks & Mitigation
  • Tooth wear or pitting due to inadequate lubrication
  • Fatigue failure from cyclic loading
  • Misalignment causing noise and vibration
  • Overheating from excessive friction
  • Backlash increase leading to driveline lash
FMEA Triads
Trigger: Insufficient or contaminated differential fluid
Failure: Accelerated tooth wear, scoring, or seizure
Mitigation: Regular fluid changes per OEM intervals, use of specified lubricants, and sealing integrity checks
Trigger: Excessive torque or shock loads (e.g., off-road use)
Failure: Tooth bending or fracture
Mitigation: Design with safety factors, use high-toughness materials, and avoid abusive driving conditions
Trigger: Improper gear alignment during assembly
Failure: Noise, vibration, and premature wear
Mitigation: Precision assembly tools, backlash verification, and runout checks

Industrial Ecosystem

Compatible With

Interchangeable Parts

Compliance & Inspection

Tolerance
Tooth profile tolerance per ISO 1328-1 Grade 6-8, backlash within 0.10-0.20 mm, surface finish Ra ≤ 0.8 μm
Test Method
Dimensional inspection via CMM, hardness testing (Rockwell C), metallurgical analysis, dynamometer testing for fatigue and torque capacity, noise-vibration-harshness (NVH) testing

Buyer Feedback

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Frequently Asked Questions

What is the difference between side gears and spider gears in a differential?

Side gears (sun gears) are connected to the drive axles and transfer torque to the wheels, while spider gears (pinion gears) rotate within the differential case and mesh with the side gears to allow speed differentiation during turns.

Can worn side gears cause vehicle handling issues?

Yes, worn or damaged side gears can lead to uneven torque distribution, excessive backlash, noise (whining or clunking), and poor handling during turns due to improper wheel speed differentiation.

How are side gears manufactured?

They are typically forged or machined from alloy steel, then heat-treated (carburized or nitrided) for hardness. Precision grinding or honing ensures accurate tooth geometry and surface finish.

Can I contact factories directly?

Yes, each factory profile provides direct contact information.

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