They're very good trannies for mild-medium buildups... Unfortunately, Choice of performance stall convertors is limited unless you get a custom one done. I run a TCI Breakaway convertor in my FMX with a Transgo shiftkit, works great for the 400 ponies I have in my Windsor...
Much more though and I'll probably swap the tranny for a AOD...
really?? i was told that the max rateing for the FMX was around 250 or so HP. but considering that my car made that stock, i didnt always believe it. i know a guy with a 390 in his old ford truck that still has the FMX in it as well. but i have also heard that the FMX parts are hard to find. a buddy of mine has a cousin that works at a tranny shop and he said that he got some HiPo parts for it, but they were quite hard to find and expensive at that.
First of all, who said only 250hp? My wife's 70 Mach 1 with a 11:1 compression 351C-4V came with an FMX, and that has (supposedly) 300hp from the factory. By the way, it isn't horsepower that you have to worry about. It is the torque handling capability.
Also, I have a buddy that is still using the same FMX tranny that came in his car originally. His car is a 71 Mach 1 that came with a 351C-2V. OK fine. Afrter going through several iterations of performance engine rebuilds to the Cleveland, where he got down to the high, high 12s in the quarter mile, he put in a 514" stroker motor. Still the same original FMX! Why? because 'they' said it couldn't or shouldn't be done. He used a bellhousing from a 351M full size wagon I had once. There have been several modifications to the trans, like a much higher stall converter, shift kit, etc, but it is still not all that far from what any weekend mechanic would do. This car is now turning 10.90s (actually a little better) in the quarter. I'd have to guess that it is putting about 500hp to the ground, easily!
The FMX has a cast iron case, so that is plenty strong, but the big plus is that it has a center support bearing for the internals. This bearing keeps the internals from flexing or bending under extreme duty. Like I said, they're just about bulletproof! Just about any of the performance aftermarket companies still have the rebuild kits, shift kits and performance converters available, they just don't advertize them any more since the FMX is pretty much gone for all intents and purposes. The one thing you cannot get for an FMX is a trans brake. I believe the last usage for the FMX was in the late 70s.
ahh, the one to tell me it was only a 250 hp part was a college intructor in a beginning auto mechanics class ( i left that for the auto body section). the part thats even worse is that hes a Ford guy. he has had a few Mustangs in the days including a 69 428 CJ back in the day ( says he sold it for like 3K back in 1980 ). it just seems i was misinformed. i havent had any problems with my tranny, so i believe all of ya.
I have a FMX in my 70 XR7 Convertible I removed it on my back with a trans jack had it rebult and put it back in.I will never do that again. It's a great Trans don't change it for a C6 or any other.In my neck of the woods you can get what ever you need for it Had mine rebult for about 500.00.The only thing I have to say about the FMX is do not do it on your back!!!!!! with or without a trans jack.I still feel the PAIN from that job. steelcat
I have an FMX with the same problem. It jumps from park to reverse on its own. I have to leave it in neutral if it's running while parked. Almost lost it once at Harve's car wash. They parked it on an incline without setting the brake and it popped into reverse and rolled back into a three lane one way street, blocking all three lanes! Luckily they pushed it out of the way before it got hit.
First off is your trans the original or has it been changed? The reason I ask is if it has been changed and came out of a column shift car the shift lever on the trans is different and the ratio is wrong for a floor shifter. Make sure that you get all the gears in the shifter, loosen the rod adj at the shifter and manually move the trans lever to park, snug the adjuster and then move the shifter lever to L and check to see if it lines up properly.
I went through the same trouble with mine as the trans was not the original. My shifter shaft seal was leaking and I decided to fix it and found out the shifter problem at the same time. I have another trans laying in the garage that came out of a floor shift car and seen the differance in the trans shift levers right away.
The column shift lever on the trans is shorter and is tilted back too far. I plan on using my other trans in the future and did'nt want to rob the shift lever shaft out of it, so since I had mine out of the trans to replace the seal I cut the lever off and welded on a new one that I fabricated to match what it needed. Getting the shaft out of the trans with it still in the car and the headers in the way is another story in itself.
If the above is not your problem and you can get the full stroke on the shifter handle then you have to start looking for worn parts. Either in the shifter itself or the bellcrank on the trans shifter shaft. I would first check the shifter itself as they are prone to wear badly. If the shaft bushings are worn out so bad they trashed the holes in the housing a nice trick is to drill them out and have a machine shop fix you up with some fitted brass bushings. mm