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1 800 255 4417 www.castrol.com/GPS Transmission Fluids Background & Properties July 2017 Types of Transmissions and Diagnosing Problems A premium TO-4 powershift transmission fluid should: • Provide control over the 7 different frictional elements, both metallic and non-metallic, commonly found in a powershift transmission; • Eliminate brake noise; • Reduce wear of elastomeric material; • Prevent slippage; • Encourage stable performance over the life of the fluid; • Inhibit metal-to-metal contact while protecting vane pumps, planetary gear sets, final drive gears and bearings from premature wear; • Offer foam protection to guard against fluid loss; • Promote low temperature performance to reduce start-up wear; • Control oxidation to prevent deposit formation that can restrict lubrication; and • Maintain excellent shear stability to ensure consistant protection from wear. Diagnosing TO-4 Type Powershift Transmission Problems Improper use of an ATF or tractor fluid in most powershift transmissions will produce burnt and/or slipping clutches, inadequate holding capacity for both brakes and clutches and insufficient wear protection for gears. Caterpillar pioneered the TO-4 specification for its off-highway powershift transmissions. Fluids meeting this specification have been factory fill on all CAT powershift transmissions since 1991, and there is little comparison between the TO-2 and TO-4 specifications. The TO-4 specification defines frictional capabilities in-depth and combined with the anti-wear properties and added gear protection, a premium TO-4 fluid maximizes powershift transmission life and operating efficiency. Some agricultural equipment such as medium and large size tractors also employ powershift transmissions. The friction material of the shifting clutches in this application are selected to function properly with tractor hydraulic fluids, which have a low static coefficient of friction to prevent chatter or squawk in the wet brakes used in these machines. Hydrostatic Transmissions A hydrostatic transmission uses fluid to transfer power from the engine to the drivetrain through a hydraulic pump and motor. A transmission of this type consists of a pump connected to the engine generating fluid power to drive a hydraulic motor, which is connected to the axle and/or driving wheels. If the displacement of the pump and motor were fixed, the transmission would merely act as a gearbox to transmit power. Most hydrostatic transmissions use a variable displacement pump or motor in order to vary speed, torque or power and provide transmission function. Therefore, the fluid used in a hydrostatic transmission only needs to function as a hydraulic fluid, as there are no clutches or gears to lubricate. Fluids commonly used in hydrostatic transmissions include hydraulic fluids, automatic transmission fluids and tractor hydraulic fluids. The owner's manual of the specific equipment should be consulted for the manufacturer's preferred fluid. D 7