Both trannys are good. The K4A you have is fairly bullet proof. The advantage of the K4C is the variable control pressure while your tranny has only 3 settings. That is the function of the solenoid on the top of your tranny. If you want to convert, I would suggest getting the setup from a boneyard. As an aside if your trans clunks harshly on down shifts, that is easilly adjusted at the little switch on the air horn.

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