Side Gears (Sun Gears): Pressure Angle 20-22 degrees

Q: 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.

Q: 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.

Q: 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.

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

Parameter	Typical range	Notes & selection driver
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

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 1328-1, DIN 3961, AGMA 2008-B01, SAE J1545

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.

View Product Details

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

Rear differential assemblies in passenger cars, trucks, SUVs, and light commercial vehicles

Typical Suppliers & Equivalents

AAM (American Axle & Manufacturing), Eaton, GKN, Dana, ZF Friedrichshafen, BorgWarner

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

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Side Gears (Sun Gears)

Manufacturer profiles associated with Side Gears (Sun Gears).

Sourcing Side Gears (Sun Gears) from China?

Tell us your specification and target quantity — we will match it against manufacturer records and come back with the factories that fit.

Request manufacturers We manufacture this

Manufacturer listings support early research and capability understanding. They are not certification, ranking, or transaction guarantees.

Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

Related Components

Clutch Disc

A clutch disc is a friction component in clutch-brake systems that engages and disengages power transmission between rotating shafts.

Synchronizers

Synchronizers are precision components in manual transmissions that enable smooth gear shifting by equalizing rotational speeds between gears and shafts.

Brake Disc (Rotor)

A rotating disc in disc brake systems that creates friction with brake pads to slow or stop vehicle motion.

Main Bearing Journals

Main bearing journals are precision-machined cylindrical surfaces on a crankshaft that rotate within main bearings to support rotational motion in internal combustion engines.

Frequently Asked Questions

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