Gearbox Oil Types

by Horacio Garcia

A gearbox is a mechanical housing that holds interconnected toothed cylinders that turn or rotate on central axes. Automobile transmissions are commonly called gearboxes, though autos usually have other gearboxes besides a transmission, such as the rear end drive and countless other parts that require gear reduction. The gears come in many shapes, such as spur, helical, bevel and worm designs. Gearbox oil is lubricant used to reduce the friction and wear between moving gears. The different gearbox oil types are determined by the different speeds the gears run at as well as the temperatures created by the friction between gears and ability of those oils to limit those temperatures.

Rust-Prevention Gear Oils

Rust-preventing gear oils are petroleum-base or mineral-base compounds which contain rust inhibitors. These gearbox oils come in two different classes, monograde and multigrade gear oil. Monograde gear oil is designed to be used at certain "normal" temperatures while multigrade gear oil can be used at warmer or colder temperatures as well as normal temperatures. The benefit of rust-prevention gear oils is that they extend the life of the gears while allowing the gears to run at high temperatures. This gearbox oil is best used in low-load gearboxes.

Extreme Pressure Gear Oils

Extreme pressure (EP) gear oils are designed as synthetic or mineral bases. The EP gearbox oil type is multigrade and has rust prevention inhibitors as well as anti-foaming additives that prevent the gear oil from thickening and losing its cooling capability. The life of EP gearbox oil is limited because of all the additives. This type of gearbox oil is best used for gearboxes that run under a lot of pressure. A lot of stress placed on the gears causes the gears to wear quicker; EP gear oil extends the life of this high-load-bearing gearbox.

Synthetic Gear Oils

Synthetic gear oil is chemical-based gearbox oil made up of polyalphaolefins (PAO), esters oils or polyglycols. Synthetic gear oils are multigrade and have every preventive additive included as part of its makeup. This gearbox oil can be run at extremely high or low temperatures. It prevents rust, foaming inside the gearbox and wear of the gears. The synthetic oil types are used in gearboxes that are run in unusual conditions such as below-zero environments, wet climates and dusty or muddy weather.

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