700R4 high performance overdrive billet servo. This Superior / Fairbanks Maximum Overdrive Servo has 50% more holding power than the stock overdrive servo. Talk about your extra firm 3-4 shift, this is it. Good for towing in overdrive. Can be installed without removing the transmission or valve body. Right picture.
* 4th apply piston and cover * Better holding capacity in 4th gear * Lip seal design on piston (less leakage) * Proper 4-3 (no drag) release * Constructed of billet aluminum