04StangSC

My dad has a 69 Mach 1 with a 351and the FMX tranny that he has in it is JUNK!! We plan on having a new one in it by next spring. What do you guys think should go in it? Pros and Cons of both the C4 and the C6.

dcohen

stick with the fmx

they are TOUGH transmissions, idk why it wouldnt work like a dream, i mean, its only 38 years old

but seriously the FMX's are good transmissions, but if you are dead set on a c4 or a c6, go with the C4

mustang monthly just did an article on c6 vs. c4 and the c4 won

remicks

+1 on the FMX, stay with that trans. Its tough as hell, lighter than a C6 and original. If it needs it, rebuild it, its worth it, you will regret switching to a C from it. But if you must go with the C4. The C6 is a heavy big block or truck transmission, its extremely durable though, but its heavier and robs more power. But for a small block like the 351 stick with the C4, its meant for small blocks and will handle around 400hp. If you are determined to swap a tranny look into an AOD/AODE, more gears overdrive. Just do a search of the forum and it will tell you everything you need for a swap.

andrewmp6

Yes rebuild the fmx or use a aod/aode

4reboy

yeah rebuild the fmx. but if u go with C4 or C6 choose the C4 like others have said. Id on't think think handle 400 hp though, more like 300 thats why ford used the FMX, because of the 351. It puts out more power, so the tranny takes more of a beating. I think ford did it right from the factory so I'd stay stick with it

BUT if u do do a C4, get it pro built so it can handle more power. the C4 is lighter though so thats one benefit of it