Ford C4/C5 Transmission Billet Intermediate Ratio C Servo 1964-1986 As used with Shelby Mustang and other performance vehicles, Sonnax "C" ratio servo kit K13259C-1 offers greater holding power, giving cleaner, firmer 1-2 and 2-3 shifts. Machined from 6061 aluminum billet, this servo features lip seals on the piston for superior sealing over a wide range of fluid pressure. This is the largest in the C4 servo family and works equally well in performance C5 applications. The servo pin incorporates two PTFE sealing rings to insure the hydraulic integrity of the pin in worn cases. Cleaning up a 2-3 flare was never easier than installing this servo.