Can anyone tell me how much horsepower a C4 takes away from the crank?

 

Not very much, its negligible versus a manual trans. Very light parts inside and a minimum of drag from the pump. Its one of the more efficient automatics. The C6 is one of the worst, and then the 4L80E, those are power sucking monsters, but they can take a masive amount of torque and not break.

Why do you want to know?

 

im ganna take my car to the dyno pretty soon and just wanted to get an idea of what horsepower id have at the crank from the readings id get taken at the wheels. just curious i guess.

 

C-4 in stock form uses about 12 hp.