TH400 Oversize Intermediate Piston and Center Support for High Horsepower Number 223704.
#66CS. TH400 Oversize Intermediate Piston and Center Support. If your TH400 transmission is being used in high power applications e.g. Supercharged, Turbocharged, Nitrous or Mega Cubic Inch engines, you need to look at every area of the transmission to boost your performance.
The intermediate clutch apply piston has been increased in size by 9.1%. The size of the center support piston and bore is .250″ larger. (stock piston is 5.617″ – this piston is 5.867″ diameter)
The increased diameter applies more clamping force on the second gear clutch pack, reducing the possibility of driving through the clutches as the power curve comes on strong.