Gear Lubrication – Basic Technical Knowledge

1. Common Types of Gears

Spur Gear: Straight-tooth gears, medium load, moderate speed.

Helical Gear: Smooth operation, high load capacity, used in automotive and industrial gearboxes.

Bevel Gear: Change of rotation direction, used in angular drives.

Worm Gear: High gear ratio, high friction, significant heat generation.

Planetary Gear: Compact, high load capacity, common in automatic transmissions.

2. Gear Lubrication Requirements

Reduce friction and tooth surface wear.

Prevent pitting, scuffing, micropitting.

Dissipate heat and maintain stable operating temperature.

Protect against corrosion and rust.

Maintain continuous oil film, provide good anti-foam and air release.

Ensure EP (Extreme Pressure) performance for heavy loads and shock conditions.

3. Determining Gear Oil Viscosity

Viscosity depends on speed - load - operating temperature (according to ISO 12925-1, DIN 51517-3, AGMA 9005):

High speed → lower viscosity oils (ISO VG 68–150)

Heavy load, low speed → higher viscosity oils (ISO VG 220–680, up to 1000)

Quick selection rule (based on pitch line velocity):

15 m/s - ISO VG 68–150

2–15 m/s - ISO VG 220–460

<2 m/s - ISO VG 460–1000

4. Reference Table: Gear Type – Application -Recommended Oil – ISO/SAE Viscosity

5. Gear Lubricants

a) Industrial Gear Oils:

For enclosed gearboxes and heavy-duty gear systems.

Standards: ISO VG 68–680, DIN 51517 CLP, AGMA EP.

Properties: wear protection, strong EP performance, oxidation stability.

b) Automotive Gear Oils:

For manual transmissions and differentials.

Standards: API GL-4, GL-5, GL-6.

SAE viscosity grades: 75W-90, 80W-90, 85W-140.

6. Gear Lubrication Methods

Oil Bath Lubrication: Simple, for small gearboxes.

Splash Lubrication: Oil is splashed around by rotating gears.

Forced Circulation / Oil Spray: Pumped lubrication for heavy loads and high speeds.

Grease Lubrication: For open gears and low-speed applications.