Spider Gears (Planetary Gears): Pressure Angle 20-22 degrees

Component Specifications

Definition

Spider gears are a set of small bevel gears mounted on a central spider or cross-pin within a differential assembly. They function as planetary gears that rotate around the sun gears (side gears) connected to the axle shafts. This configuration allows the left and right wheels to rotate at different speeds while maintaining torque distribution, crucial for vehicle stability during cornering and on uneven surfaces.

Working Principle

The spider gears operate on the planetary gear principle within the differential carrier. When the vehicle moves straight, the spider gears rotate with the differential case but do not spin on their own axes relative to the side gears. During turns, the outer wheel must travel farther than the inner wheel, causing the spider gears to rotate on their axes, allowing the side gears (and thus the wheels) to rotate at different speeds while torque is distributed equally.

Materials

Typically made from case-hardened alloy steels such as SAE 8620, SAE 8822, or similar grades with surface hardness of 58-62 HRC and core toughness. Advanced applications may use powder metallurgy steels or surface treatments like carburizing, nitriding, or shot peening for enhanced durability.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Mounting	Cross-pin or spider shaft
Lubrication	Hypoid gear oil (SAE 75W-90 typical)
Module/Pitch	2.5-4.0 mm (varies by application)
Tooth Profile	Straight or spiral bevel
Pressure Angle	20-22 degrees
Number Of Gears	2 or 4 (depending on differential type)

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, DIN 3961, AGMA 2008, 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.

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Engineering Analysis

Risks & Mitigation

Tooth pitting and spalling due to fatigue
Wear from inadequate lubrication
Overheating from excessive load
Misalignment causing premature failure
Corrosion in contaminated environments

FMEA Triads

Trigger: Insufficient or contaminated lubricant
Failure: Accelerated wear, scoring, and eventual tooth fracture
Mitigation: Regular maintenance with specified gear oil, use of magnetic drain plugs, and proper sealing

Trigger: Excessive torque or shock loads
Failure: Tooth bending fatigue or breakage
Mitigation: Proper gear material selection, heat treatment, and design for application torque requirements

Trigger: Misalignment during assembly or housing deflection
Failure: Uneven load distribution and localized wear
Mitigation: Precision machining of housing, proper bearing preload, and alignment verification during assembly

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

AGMA Quality 10-12 for tooth profile, ISO 1328 Class 7-8 for gear accuracy, backlash typically 0.10-0.20 mm

Test Method

Coordinate measuring machine (CMM) for geometry, hardness testing per ASTM E18, fatigue testing per SAE J1545, noise/vibration analysis

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

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Manufacturers of Spider Gears (Planetary Gears)

Manufacturer profiles associated with Spider Gears (Planetary Gears).

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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

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Frequently Asked Questions

What is the primary function of spider gears in a differential?

Spider gears enable the left and right wheels to rotate at different speeds during turns while maintaining equal torque distribution, preventing wheel hop and ensuring smooth cornering.

How many spider gears are typically in a differential?

Most passenger vehicle differentials contain either 2 or 4 spider gears mounted on a cross-pin, depending on the differential design and load requirements.

What happens when spider gears fail?

Failed spider gears can cause binding, noise (whining or grinding), loss of torque to one wheel, or complete differential lockup, potentially leading to drivability issues or vehicle immobilization.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Spider Gears (Planetary Gears)