Hey everyone,
I apparently have the FMX transmission instead of the c4 in the 79 ranchero. Does anyone know anything about the FMX tranny? I've heard more bad than good, but i read somewhere they can handle a lot of horsepower. As far as gearing, is it the same as the c4 and c6? For performance purposes, what's the main difference other than weight? And could the transgo shift kit help it? I want it to perform well on the street, but be able to do well at the strip. Its about a 320 horse motor with 3.70 gears in the auburn pro 9 inch limited slip. Ive also taken out a lot of weight on this sucker.
Thanks!
Danny

 

Danny, The FMX is older technology. The trannys can work for many years trouble free. For dragracing, the tranny is heavier with it's cast iron middle, so you might want to look at a lighter unit.

John

 

go with a c-6

 

Due to having my engine balanced with the flexplate, i think i will go with a c4 because i dont want to have to pay and bring everything back in to get it balanced (my flexplate is a counter balanace). If the flexplate also works for a c6, then tell me now! But anyway...Has anyone converted their transmission from the FMX to a C4 on a 79 or similar Ranchero (i have a 302 in mine)? I want to see what all I will have to do. Are the 2 trannys the same length, or will i have to buy a new driveshaft? I know a new torque converter, but im not sure about anything else. I was thinking about the TCI c4, but it doesnt come with a bellhousing. Are FMX and c4 bellhousings (small bellhousing) interchangeable? If i can go the c6, then i know i wont have to worry about that. So if anyone has done this before, I would greatly appreciate it. One more thing, i heard something about changing the transmission cross memeber? For a c4 would i have to? Thanks again!
Danny

 

Have you considered using an AOD or AODE instead of the C class trannys? The benifits are that the tranny has overdrive and is alot lighter than the C6. The C6 is heavier duty than the C4 but its more costly and its heavier. Since both the C4 and C6 have the same gearing, theres no reason to suffer with the extra weight. The Ranchero is a heavy car so it needs all the help it can get. Also keep in mind that since it is a heavy vehical your tranny will be put through alot of stress ESPECIALY if your going to be racing at all. Make sure that C4 is really beefed up, its taking alot of brunt from the engine itself and the task of pushing that 3400lbs+ car/truck down the road. C4's were mainly used in light V8 applications. They are best suited for Falcons, Mustangs, Pinto's, Rangers. C6's were used as well as the FMX in the larger cars like LTD's, fairlanes, Rancheros, and in the full size trucks at that time. Hell C6's were used all the way into the late 80's if im correct. The AOD has shorter gears and isnt as heavy as the older automatics. Plus its cheaper to get ahold of an AOD and beef it up.

Just my two cents worth.

 

As far as the FMX transmission goes it is probably the strongest and most durable made. The weight is the biggest issue in that for racing the weight is a deterrence. For all around use though the FMX could not hardly be destroyed.

 

I am planning to swap the FMX in my 78 Ranchero (built 351W) for a C6. Primary reason is the MUCH greater supply of torque converters available for the C6. Also, I got a great deal on a small block C6 locally. In it's basic mode (plus a Transgo kit) it can more than handle anything this combo can dish out.

-jwk-

 

the c4 will fit your fmx flexplate.the later ones anyway.some early ones took a small flywheel.the c4 is the same lenght as your fmx.big cars and trucks had a longer one.you will have to change your front yoke.if your fmx is good i wouldnt bother.

 

I always junked any FMX I ever had. For small block use a C-4 is very peppy and will take alot of abuse. The gearing in the C-6 robs alot of power out of a small block. If you are on a budget (most of us are) I would leave it until it leaves you then replace it with a tranny of your choice....