Common Gear Types Don’t Forget the Gear Oil Gear oil is often overlooked when it comes to scheduled maintenance.

Gear Oil Basics additives in order to reduce wear and High-quality gear oil must lubricate, extend gear and bearing life. cool and protect geared systems. Additional Differences It must also carry damaging wear Because many of the components debris away from contact zones and found in the drivetrain consist of ferrous Spur gears Straight muffle the sound of gear operation. material, the lubricant must prevent Bevel Gears Differential, standard transmission and Transmissions rust and possible corrosion to other industrial machinery gears often require Industrial Equipment materials. Rust and corrosion problems extreme-temperature and pressure Some Differentials are not nearly as prevalent in engines. protection in order to prevent wear, pitting, spalling, scoring, scuffing and The many small and intricate other damage that result in equipment components that make up gear failure and downtime. Protection against sets can be quite noisy and may oxidation, thermal degradation, rust, be subjected to shock-loading. The copper corrosion and foaming is also viscosity and extreme-pressure important. formulation of gear oil quiets gears and dissipates shock-loading. Gear Oil and Motor Oil Are Not the Same The rotating motion of the gear sets also Gear oil differs from motor oil. While tends to churn the lubricant, leading Spiral Bevel Worm to foaming. If a gear lube foams, its Gears Gear Set many motorists may assume SAE 90 gear oil is thicker than SAE 40 or 50 load-carrying capacity is significantly Industrial Equipment Gear Reduction motor oil, they are actually the same reduced because the air suspended Some Differentials Boxes viscosity; the difference is in the within the oil is compressible. For additives. example, when the gear teeth come into contact with each other, any trapped Motor oil contains additives such as air bubbles compress, reducing the detergents and dispersants to combat thickness of the separating oil film. In byproduct chemicals from gasoline turn, this reduction could lead to direct or diesel ignition. Because an internal metal-to-metal contact between gear combustion engine has an oil pump teeth and result in accelerated wear. and lubricates the bearings with a The gear oil must have the ability to hydrodynamic film, extreme-pressure dissipate this entrapped air, ensuring a additives such as those used in gear sufficient lubricating film that protects oils are not necessary. Hypoid gears Planetary the gears against contact wear. Gear Set Motor oils and gear oils both have Differentials Typical Drivetrain Fluid Additives anti-wear additives, and they both must Transmissions Much like with motor oil, the additives lubricate, cool and protect components, included in a gear oil formulation either but gear oils may be placed under enhance existing properties or impart extreme amounts of pressure, creating new ones. Drivetrain fluid additives a propensity for boundary lubrication, a include the following: condition in which a full-fluid lubricating film is not present between two rubbing • Extreme-pressure and anti-wear surfaces. For example, differentials in agents minimize component wear cars and trucks have a ring-and-pinion in boundary lubrication situations. hypoid gear set. A hypoid gear set can experience boundary lubrication, • Pour-point depressants improve pressures and sliding action that can low-temperature performance. Helical gears Herringbone wipe most of the lubricant off the gears. • Rust and corrosion inhibitors Gears To combat this extreme environment, protect internal components. Transmissions extreme-pressure additives are Transmissions incorporated into the oil. AMSOIL • Oxidation inhibitors reduce synthetic gear oils are formulated with the deteriorating effects of heat, an extra treatment of extreme-pressure increasing the oil’s service life. • Viscosity index improvers allow a Hypoid Gear Lube (SVO), 80W-90 Synthetic Gear lubricant to operate over a broader Hypoid gear sets are a form of bevel gear, Lube (AGL), 75W-90 Long Life Synthetic temperature range. but offer improved efficiency and higher Gear Lube (FGR) or 80W-140 Long Life Synthetic Gear Lube (FGO). • Anti-foam agents suppress ratios over traditional straight-bevel gears. foaming tendency and dissipate Commonly found in axle differentials, Most manual transmissions have entrapped air. hypoid gears are used to transmit power helical gears that do not require GL-5 from the driveline to the axle shafts. performance. The helical gear is almost • Friction modifiers - The required a straight-cut gear, but on an angle. degree of friction-reduction can Planetary There is spiral action and very little sliding vary significantly between different Planetary gear sets, such as those found action, and there is less need for extreme- pieces of equipment in drivetrain in automatic transmissions, provide the pressure additives. GL-4 gear lubes applications. In some cases, friction different gear ratios needed to propel provide less extreme-pressure additives modifiers may be required to obtain a vehicle in the desired direction at than GL-5 lubes. the desired results. the correct speed. Gear teeth remain in constant mesh, which allows gear In manual transmissions using helical Gear Design Dictates Lube Design changes to be made without engaging or gears, AMSOIL typically recommends Gear designs vary depending on the disengaging the gears, as is required in either Synthetic Synchromesh requirements for rotation speed, degree a manual transmission. Instead, clutches Transmission Fluid (MTF) or Synthetic of gear reduction and torque-loading. and bands are used to either hold or Manual Transmission and Transaxle Gear Transmissions commonly use spur gears, release different members of the gear set Lube (MTG). while hypoid-gear designs are usually to get the proper direction of rotation and used as the main gearing in differentials. gear ratio. AMSOIL Provides Gear Oil Options Common gear types include the AMSOIL offers premium synthetic following: Helical drivetrain lubricants to meet the needs of Helical gears differ from spur gears in that nearly every application. The synthetic Spur their teeth are not parallel to the shaft axis; base stocks and top-quality additive Spur (straight-cut) gears are widely used they are cut in a helix or angle around packages found in AMSOIL gear lubes in parallel-shaft applications, such as the gear axis. During rotation, parts of and transmission fluids provide the transmissions, due to their low cost and several teeth may be in mesh at the ultimate in wear protection for cars, high efficiency. The design allows the same time, reducing some of the loading trucks, outboards, heavy-duty and racing entire gear tooth to make contact with characteristics of the standard spur applications. the tooth face at the same instant. As a gear. However, this style of gearing can result, this type of gearing is subjected to produce thrust forces parallel to the axis high shock-loading and uneven motion. of the gear shaft. To minimize the effects, Design limitations include excessive noise two helical gears with teeth opposite each and a significant amount of backlash other are used, which helps to cancel the during high-speed operation. thrust out during operation. Bevel Herringbone Bevel (straight- and spiral-cut) gears Herringbone gears are an improvement transmit motion between shafts that are over the double helical gear design. at an angle to each other. Primarily found Both right- and left-hand cuts are used in industrial equipment, as well as some on the same gear blank, cancelling out automotive applications (differentials), any thrust forces. Herringbone gears are they offer efficient operation and are easy capable of transmitting large amounts of to manufacture. As with spur gears, they horsepower and are frequently used in are limited due to their noisy operation at power transmission systems. high speeds and are not the top choice where load-carrying capacity is required. Differences in gear design create the need for significantly different lubricant Worm formulations. For instance, hypoid Worm gear sets employ a specially gears normally found in automotive machined “worm” that conforms to the arc differentials require GL-5 concentration of the driven gear. This design increases and the performance of extreme-pressure torque throughput, improves accuracy additives due to their spiral sliding action. and extends operating life. Primarily In differential applications that use hypoid used to transmit power through non- gears, AMSOIL typically recommends intersecting shafts, this style of gear is one of the following: Severe Gear® 75W- frequently found in gear-reduction boxes 90 Synthetic Gear Lube (SVG), Severe as it offers quiet operation and high ratios. Gear 75W-110 Synthetic Gear Lube Its downfall is its low efficiency. (SVT), Severe Gear 75W-140 Synthetic