Functions of Automatic Transmission and Tractor Fluids

Noria Corporation

Functions of Automatic Transmission and Tractor Fluids

Automatic transmission fluids (ATFs) are among the most complex lubricants available because they must serve so many functions in the transmission, including heat dissipation, wear protection, lubrication, foam prevention and shift quality.

ATFs must also be compatible with all of the complex transmission components and materials, such as seals and friction discs, operate at both high and low temperature extremes, and maintain good performance for thousands of miles.

Many of today's engine oils use organic nitrogen compounds in the detergent/dispersant additive package. This is done to reduce the sulfated ash residue in engines that result when metallic type detergents are used. These nitrogen compounds can have negative effects on transmission oil seals, causing them to shrink or swell excessively and then leak.

A more serious problem is that these nitrogen compounds can cause the transmission friction materials to become brittle, flake and/or break away from the disc. As a result, engine oils are no longer acceptable for use in these newly designed transmission systems because of the probability that they may contain nitrogen compounds in the additive package.

The possible adverse reactions caused by the inclusion of friction modifiers and/or nitrogen compounds can dramatically shorten the life and affect the operation and durability of these new transmission systems.

With the advent of new machinery designs, new material development and application, new additive chemistry and increased machine loads and speeds, the necessity of stocking more specially designed lubricants for unique applications or special machine use is something for which industry must be prepared.

While ATF performance is defined by various automotive and manufacturer specifications, a large percentage of the fluids produced may be used in applications other than automotive transmissions. These include powershift transmissions in off-highway construction and mining equipment, power steering systems and rotary screw compressors.

Tractor fluids are used to lubricate transmissions, final drives, wet brakes, wet clutches and hydraulic systems usually from a common reservoir on an agricultural or industrial tractor. The unique performance characteristics of these fluids also make them acceptable for use in both on and off-highway commercial transmissions as well as some high-pressure hydraulic systems.

Because of this versatility, these lubricants are frequently referred to as UTTOs (universal tractor transmission oils). However, caution must be used before applying these oils to some of the new transmission systems because of the new friction, seal and hose materials now in use.

Remember, it is always wise to consult both the equipment manufacturer and the lubricant supplier before applying an oil that may cause compatibility problems.

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