Vehicles with Ford C6 transmissions often display stacked upshifts, no kick-down, little or no line rise and/or direct clutch failure. These concerns are frequently caused by wear of the transmission case at the modulator valve bore due to continuous oscillation of the steel valve within the bore. As wear progresses, line pressure and TV pressure are allowed to cross-leak or exhaust, resulting in these driveability problems. Salvage the case and restore normal shift operation by reconditioning the bore and installing Sonnax oversized modulator valve kit 36833-01K.