Transmission Fluids
Background & Properties
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May 2025
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Important Transmission Fluid Properties
Automatic Transmission Fluids (ATFs)
ATFs must be able to hold loads and encourage smooth shis. erefore, ATFs have a high dynamic coefficient
of friction with a moderate static coefficient of friction. ATFs do contain friction modifiers, which translate to
moderate static friction to avoid harsh shis.
Automatic Transmission
Fluids
Sliding Speed Decreasing
Torque,
Nm
TES-389
TO-4 Fluids
e most dramatic friction characteristics are found in the TO-4 fluids for powershi transmissions. TO-4
fluids have the highest static coefficient of friction for fast lock-up and outstanding holding capacity. e
chart depicts this fact with its sharp upward point illustrating a tight, firm lock-up.
Powershift Transmission
Fluids
Sliding Speed Decreasing
Torque,
Nm
TO-4
D4
Medium
Static
Friction
►
Very
High
Static
Friction
►
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