Whats the difference?
 

what is the difference between a c4 tranny and a c6.

The C4 was the small light duty automatic transmission. Units were strengthened in 1970 and are considerably stronger than those built before 1970. The C4 can be rebuilt to very tough standards and it is very light, making it popular with small block drag racers. Lots of aftermarket performance kits are available for the C4.

The C6 was ford's heavy duty unit and was most often found behind big blocks, or high performace small blocks. The C6 is considerably larger and heavier than the C4 but it is pretty tough from the factory and can be made virtually bullet proof.

Both units are aluminum case transmissions as opposed to the FMXwhich was a medium duty cast iron case transmission.

That pretty much exhausts my C4/C6 knowledge.

thanks. i was just curious. i am going to get a new c4 from performance automatics to put behind my blown 427 stroker.

Make sure you spend the big bucks and get the BEST one they have. You will need it for a C-4 to live behind that engine. It can be done though! Have one behind a 750 H.P 347 small block and it runs in the 9's in the 1/4 mile with no problems after 1-1/2 years. Do have to "freshen" them up once a year though. But that is a drag car. not a street car. Also get the biggest trans cooler that you can run as it is the heat that kills these transmissions.

A c4 has a removable bell houseing, where as a c6 is all one piece. I'm sure u could put a c4 behind a 427, but personally, I use a c6.

im using the super comp c4 from performance automatics with the built in tranbrake. i thinks its rated at 700hp

Should work fine, especially on street tires as the torque load on the trans will be limited by the lack of traction. With slicks it is a different story, All of that torque twisting thru that big block can certianly cause some concern. The 750 H.P. 347 that we run the C-4 behind does not make the kind of torque that a big block would, this is all high rpm power, not the bottem end grunt of a big block.