I am building a slightly modified street rodded 50 ford F1. It has a 302, 9" rear, and auto FMX tranny all from a 68' mustang. My question is should I keep the FMX or trade for a C4? There is nothing mechanically wrong with the FMX. I just haven't seen much for speed/performance parts for the FMX's. I would like to hear from FMX and C4 owners on the pros and cons of each tranny. Any ideas/suggestions are greatly appreciated!

 

I've had recurring problems keeping a second gear in my fmx. I run a 351 C in my 56 and have lost second three times now a two speed dont get it!!

 

I guess it depends on what you want to do with the transmission. The FMX has it's origins in the Cruise-o-Matic of the late '50s. It's overbuilt internally, so it will take a tremendous amount of punishment. It was usually, but not always, used in heavy duty or V8 applications, and will bolt up to any of Ford's V8's. On the flip side, it's a bit of a slushbox, IMHO, it's not easy to rebuild and it's incredibly heavy. It's production history overlapped the C6, but it was eventually replaced by the C6.

The C4 appeared first in '64 in lighter duty appications, i.e., in Falcons and Mustangs, behind 6 cylinders and small block V8s. To my knowledge, you can't put one behind any of Ford's big block engines. That said, it's a very durable transmission and very easy to rebuild, as automatics go.