Issue link: http://read.dmtmag.com/i/859318
Transmission Fluids Background & Properties castrol.com/GPS 800 255 4417 May 2025 GPS Important Transmission Fluid Properties Automatic Transmissions An automatic transmission uses electronically- or hydraulically-controlled friction clutches to select gears. Although easier to operate, automatic transmissions sometimes require more maintenance. Automatic transmissions typically require an automatic transmission fluid. Premium automatic transmission fluids (ATFs) are designed to: • Prevent metal-to-metal contact and wear; • Promote efficiency in vane pumps, planetary gear sets and bushings; • Maximize fuel economy; • Allow low temperature operation; • Control oxidation to guard against oil thickening; • Provide correct frictional properties for shiing clutches; • Be compatible with seals; and • Protect against thermal degradation. Diagnosing Automatic Transmission Problems Problems associated with automatic transmissions can sometimes be traced back to the fluid. Using a TO-4 fluid in an automatic transmission will result in harsh shis, poor low temperature performance, mediocre transmission response, sludge and deposit formation and copper and bronze corrosion. Using a tractor fluid in an automatic transmission will oen cause burnt shiing clutches, elongated shis, inadequate holding capabilities and sludge and deposit formation. An automatic transmission operating with an improper fluid will increase the likelihood of shortened component life, unscheduled downtime and elevated maintenance costs. Fluid choices for automatic transmissions should take into account severity of service, ambient and operating temperatures, which will influence viscosity grade selection, and any OEM-required approvals. For example, Allison prefers a TES-295 fluid for severe or extended service automatic transmissions, a TES-353 fluid for its more severe, off-highway automatic transmissions and a TES-389 fluid for its lighter duty and standard service, on-highway automatic transmissions. Once the fluid type and grade is established, choosing a quality ATF will enhance transmission performance and component life while decreasing costly downtime. Powershi Transmissions e powershi transmission has some internal components similar to that of the automatic transmission, but with some key additions. e control of the powershi transmission is manual and allows for a wide range of speed ratios with an almost instant shi from forward to reverse. Most powershi transmission fluids have evolved from motor oil and multi-viscosity recommendations to straight weight TO-4 transmission fluids. is fundamental shi in fluid type was prompted by the design of the powershi transmission itself. Today's powershi transmissions have highly sensitive friction-based components that require a "grabby," not slippery, fluid to achieve a tight lock-up. D6 ecastrof