the truck i just purchased has a fmx behind the 351 windsor i was wondering how strong these tannsy are. do they hold up well to any high performance use at all .i can only find shift improver kits but know high performance stall convertors ,will a c-4 be a better choice or evena c-6 or should i just keep the fmx

 

C-6 is stronger, but ford put 4v Clevelands in front of FMXs, you likely wont destroy it as long as you use Type-F fluid.

 

is the c-6 a direct replacment for the fmx or what do i need to know when doing a c-6 swap

 

the C-6 is a direct swap. same length, same yoke. swap coolant lines only.

 

I've always been a fan of the FMX ever sense I blew up (ok...I stripped out) 2 C4's behind a 351w. One of the instructors had an old FMX out of a Merc. So I installed it into my old 'beater project' car. Needless to say, being young and a lead footed driver at the time? The FMX didn't even flinch after all the abuse I threw at it. Where the C4's failed? The FMX came out on top. Not sure how the FMX would compare to a C6 transmission however. But it's got some stout parts and construction.

S-

 

it is a borg-warner trans with roots in the 50s. it is tough, but takes more HP to run than the more efficient but tougher C-6.