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Discussion Starter #1
I am going to put in my 351w in this fall and I was thinking of installing a C-4 from a 302 Granada that I already have. I was told that I would need to beef it up (?) and put in a stage 2 shift kit to get the max performance out of it as well as a 2800 stall converter for a total price of approx. $2000 US. I have an opportunity to purchase 1) an FMX out of a 1970 Cougar (351c) with a stage 2 in it or 2) a C-6 out of a F-250 with a stage 2 shift kit for $200 each. They are both apparently in good shape and are being sold by fellow ford nuts. I would still have to buy a stall converter (about $300). Would the FMX or the C-6 bolt up to my 35w housing? Would it fit under a 66? Too long? Too wide? Overkill? Both tranny's were on small blocks previously. The C-6 on a 302 and the FMX on a 351c. Any help or suggestions would be appreciated! Thanks
 

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I ran a C-4 in my '68 coupe with a 400HP 351W. The original C-4 blew after rebuild and adding a shift kit when I took it for a test drive, a "ring" (not sure) broke producing a seemingly huge cloud of smoke and no forward motion. The shop fixed it again with the expectation that the tranny would break again sooner than later. I only ran street tires that required a gentle touch from a dead stop and never really challenged the tranny with slicks; after a year I put a mild 289 in and sold the car. I never felt that anything other than a stock torque converter (approx. 1,950 RPM) was needed for street use.

My sense is that for racing a built for racing C-4 would be perfect (light etc.); for street use a C-6 might provide bullet proof performance and longevity. Only a few small block C-6's were made and were used behind 351W's and 351C's. I don't know about the FMX's, they were never a consideration for my application. I also do not know about fitment of a C-6 in you 1966 chassis.
 

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C4....

Run a stock blueprinted one in the race car and have beat the sh*t out of it over the last 2 decades off and on...no complaints...

Light and efficient....

Your later C4 will have the larger input shaft (mine is a '65 with the little input)....can't say about clutches, etc, but that's all easily taken care of when rebuilding...

BTW, I put a grand total of under 100.00 into my early core...I do work for a trans wholesaler and we horse-traded a bit...*G* Biggest expense IIRC was the solid intermediate band and HP clutches....

Both C6 and FMX will bolt up....tunnel fit with the C6 will be tight...I couldn't run one in the race car with the engine set back 2", with the stock tunnel.

Have fun...!
 

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I put in a C4 shift kit - very simple and it chirps rubber during 80 mph 2nd-3rd shifts. Hard shifts with that much horsepower and no shift kit will prematurely wear your clutches. My W is maybe 350HP and the C4 w/ good components and the larger input shaft has had no problems, and I've read from credible sources (like VMF) that 500HP can be handled. Put a drain plug in the pan when it is open. From my reading, FMX & C-6 are big heavy suckers that'll just barely squeeze in there - you don't need the weight or aggravation. Last comment - if you go above 3.25 gears and do much highway driving, consider a built AOD before putting $$ into anything else unless a top loader is in your future.
 

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Small block C6's are easy to find. Go to any junkyard and look at trucks. 300 cu. in sixes used them too, along with 302's and 351W. Easy find.
 

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I would shop around on that $2000 figure. Should not take that much to get a strong C4 unless it's a totally new unit. And stick with the C4 or if you are in upgrade mode you should really consider an AOD.

The C6 and FMX are heavy beasts and not necessarily stronger given todays building options.
 
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Here's my long opinion. First, there's no aftermarket for a heavy FMX, lose it. Second, the C-6 is a big, cumbersome, power robber that I have never seen the need for. Third, after destroying over 30... yes 30 C-6's, one every other run, in my drag car, I opted for a Performance Automatic Super Comp C-4... 9 years ago. My car makes 711 HP @ 7000 & 613 Ft. Lbs. @ 5500... off the bottle. That plus another 400 shot on top & I have never had a problem running it in the 8's & using the trans brake. $2K is a tad high for a trans & converter as well. A good fresh, late C-4 with a good shift kit & a good intermediate band can be built yourself for less than $300 & the converter is about the same. A thou out the door should make a good tranny. By the way I run a 460 in my drag car...
 
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consider a built AOD before putting $$ into anything else unless a top loader is in your future.

Sorry to change the subject. But I thought c4/c6 had the same final drive ratio as the toploader , thus producing about the same cruising RPM ?? Am I right? Sorry to be off topic.
 

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the c4 is your best bet. Basically the parts that wear out and brake are not sifnificantly different in the c4 and the c6. The larger gears might be ideal for a dump truck but overkill of a car. The other significant factor is how wide your rear tires are. If your running what will fit the standard wheel wells then there is especially no reson to go to a larger c6
 

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still another option is the little known about C5 - which is basically a truck C4, similar in appearance and dimensions but stronger (stock-wise) on the inside. Check the 1970s and later trucks at the junkyards - you might come across one of these little "power handlers"....

randy
 

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Final drive in all the discussed trannies is 1:1 (c4, c6, fmx, toploader, t10, etc). Yeah, I noticed that comment, too /forums/images/icons/smile.gif

Hopefully, I'm going with a tremec!

Thespazardman
 

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In passenger cars from 1977 to 1978 the Toploader was offered with an overdrive 4th gear. A typical car that used this box was the Ford Granada. It looks identical to a regular toploader. You could actually take the gears from these boxes and retrofit early boxes to make a trick overdrive setup. These had a cast iron case. These were made partially by Tremac Corp. and were the start of the new Tremac coding of 170F series. Ratio: 3.29 1st, 1.84 2nd, 1.00 3rd, .81 4th.
 
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