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Discussion Starter · #1 ·
List,
An opportunity has just risen for me to purchase a c-4 or a c-6 transmission to put behind my 351 C. My qeustion is this. Will a c-4 bolt up to the 351C without headaches or do I need to go with the C-6? what years are good donors for the c-4? I am looking at buying out of a 80 mustang. Also what are good donors for the c-6. By the way this is to replace a badly burnt FMX in my 68 cougar. Any help would be appreciated
 

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C4s adaquate for 351 IF its the BIG C4 like this one is
 

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A C4 from a 68 Cougar would be ideal. You want one with floor shift provisions. Be careful not to get one from a 6 cylinder Mustang, they are weaker internally in stock form.
 

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Discussion Starter · #4 ·
ray,
tjis particular C-4 is coming out of a 72 mustang... I thinik it should work, but not so sure I will take a print of this pic and take it with me
 

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What's the tag number?

A '72 Mustang tranny is virtually identical to a '68 Cougar tranny as far as your application goes. There were some internal revisions in 1969 but the important factor for you is that 1972 Mustangs had floor shift.

You don't want to use one from a 1972 Mustang six cylinder as they are weaker internally.
 

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I recommend the BIG C4 over the small one for the larger convertor and the bigger flex plate which is easier on starters. Notice in the pic where the case joins the bellhousing, that indicates a BIG C4. This one shown is a C9 out of a 72ish Torino or similar
 

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Another thing to consiter is if you plan to run headers, many do not fit with a C6. But FMX and C4 you will have a bigger selection. C4 being the smaller of the 3.
 

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Ray,
Is there a specific application or tag number for this "Big" C4? I have seen a lot of 67 - 73 C4's and they all look identical externally (to me at least) whether 6 cylinder or 302. Are you sure you are not talking about the C5 transmission used in late 1970's to early 1980 Ford trucks? It is a beefed up version of a C4.
 

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From what i gathered a c4 isnt that strong to put behind a 351c cause not many 351c`s came with a c4(if i remember none actually)The power that a 351c produces wouldnt be able to handle the load and torque of a 351c can withstand.I seen alot of the cars with 3 types a c6,fmx and a toploader 4 speed.If you want something to cruise and have fun with go with a AOD. talk to mark piechowski [email protected] he builds transmissions for a living and is a AOD expert.How do i know this? Ask the many members of the sunshine state cougar club n you`ll hear nothing but compliments from them.
thanks
pat
 

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Royce
From what I can tonight in the dark the blue one pictured has these #s
On top of case BIG letters X14A
on side servo cover passenger side C9ZP
on drivers side of main body D3OP
and from the serial # stamp pad 7W 170456
Looks to me based on what I know about serial #s this must be a 77 trans out of a Ford serail # 170456. I don't know what the W stands for however it is currently bolted to a 351C 2V 72 vintage I believe. Its a modified or custom engine I got from someone a few years ago that was "supposed" to be good.
This particular trans has the pan that the dipstick tube threads into. The BIG C4s I have seen are in large cars like Torinos and such in mid 70s. Notice how the body flares up into the bell housing. Mustang trans or the small body and I believe there might be two small bodies the trans does not flare its more like a definate transistion not smooth like one shown. Its too dark now but I don't mind taking pix of the other C4 I have that is smaller than the one shown allthough I am not convinced its the small of the three. I believe I have the BIG and the mid size C4s and that there is another C4 that uses a small bell and ring gear 157 tooth and not the 164 tooth which I believe is what the 289 302 Cougars got (157).
The C5s as far as I know are the FM FX FMX trans aka cruise o matics merc o matics and such. Cast iron case aluminum bell, allthough your description may well be right.

The big/midsize c4s were in Econoline vans 68-74 as well allthough I can not be sure it was same as the blue one in fact I kinda doubt it offhand tonight.
I don't own any cars with C4s and while I have rebuilt them and had my turn with them its been many years since I owned anything with a c4 so the grey matters a little foggy. Everything I own now is FMX C6 or 4 speed and I'd sure like to sell that C and the two C4s I have left ,lol
I'll dig thru my books and see if I can solve any more of this puzzle
 

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A C5 is a beefed C4 with lockup torque converter.....

No, the C5 is a beefed C4 used behind 6 cylinders and 302's in Ford trucks and vans. It shares some parts with the C4 It has no relation to the FMX.

I have run a C4 behind a 351W with no problems as have many other folks, the 351C is no more powerful than a 351W. Lets hear what Mark P has to say, hopefully one of you Sunshine State folks will get him over to comment on this.

I think an AOD is fine but pretty difficult to set up and more expensive to buy and rebuild initially.

Here's a history of Ford transmissions from http://www.baumannengineering.com


In past 35 years Ford has produced many different rear-wheel-drive automatic transmissions, most of which have been introduced since 1980. The following list outlines a brief chronology of Ford Motor Company’s modern automatic transmissions followed by descriptions of some of the more complicated members.

The FMX/Cruise-O-Matic three speed evolved from the 1950’s Ford-O-Matic and was used until 1980 when the AOD was introduced.

In 1964, the C-4 was introduced, providing a lightweight and durable three-speed automatic which is a favorite among racers today. The C-4 was produced until 1982, when it was replaced by the C-5.

The C-6 appeared in 1966 as a heavy-duty unit primarily used behind big-block engines or in large vehicles. Internally, it is much like a scaled-up C-4. The C-6 is still used today in certain truck applications.

The French-built C-3 was first used in 1974 in the Ford Pinto and remained until the Merkur XR4TI was dropped in 1989.

The Automatic Overdrive (AOD) transmission was introduced in 1980 as Ford's first four-speed automatic overdrive transmission (a.k.a. AOT or FIOD in some literature). Internals are loosely based on the FMX. The AOD was finally replaced by the AOD-E/4R70W in 1994 for all remaining applications.

1982 brought the C-5 which was essentially a stronger C-4 with a centrifugal torque converter lock-up clutch and an enhanced valve body for smoother shifting. It was produced through 1986 and was completely replaced by the AOD.
 

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It's been a while since I rebuilt a C4 however I do remember there are HD and reg duty bands. I imagine all the seals,gaskets and clutches are same. Kits don't include bands. I do agree many have used C4s behind 351s as Ford did. My reason for suggesting the BIG C4 is to gain advantage of the bigger convertor and flex plate bell housing so that the "correct" 351 sized 164 tooth flex plate can be used. I hafta think if the small C4 was good behind a 351C/W then Ford would not have gone to the bother of making a BIG C4 for cars vans and larger applications. I'll see what I can do about snappin and postin pix of the smaller C4 I have.
 

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Ray,

I think the bigness is all in the flexplate and bellhousing. Ford went to a bigger ring gear size on small blocks some time in the late 1970's to reduce wear on the starter teeth. This was in all products using a C4. Not something I have any personal experience with though, I try to keep everything '67 - 68 around here if possible to avoid confusion.

I have been in contact with different size intermediate servos and know that there are different width clutch hubs for 6 cylinder or 8 cylinder due to different number of clutch plates. Seems like I took out an H servo and installed a C servo or vice versa, it was a long time ago. In any case there is a bigger intermediate servo available that applies more pressure to the band during engagement, I believe it was made by Scott Drake. I bought it from Dallas Mustang.

Sometimes I actually avoid confusion, other times not.
 

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the big C4 was used originally in the truck line for light duty pickups and econolines as was already noted. they are easy to spot due to the flared design of the main case and the fact that the bellhousing is not held on by the front pump bolts as the regular C4 is. these actually came out about 1965 or so in the econolines (had one in my 65 econoline with the HIPO 289, it worked well!). the heavy duty design made for trucks turned out to be just the ticket for the heavier intermediates in the mid 1970's and they ended up behind all V8 engines except the 400 and 429/460 at one point or another during the 70's. the bellhousing for a 351M is actually valuable as the guys with 429's buy them so they can run C4's in their race cars. if you find one of these bellhousings be sure to grab the matching block plate and put it on ebay. they always bring 100.00 or more! the heavy duty trans is a C4 but does have some other odd features like the larger flywheel already mentioned. they usually have more clutches and i have been told by a trans guy that they had some oiling refinements to help keep them cool. hawkrod
 

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68alleycat, Is there some pressing reason you don't want to just rebuild your FMX? The good parts are still out there and are readily available, just the speed shops don't advertize them. The FMX is much stronger than a C-4 in stock form.

Hawk, The same thing goes for the FMX bellhousing put behind 351Ms. My buddy is using his original FMX trans that came in his 71 Mustang Mach 1 351C-2V, but now sports a 484-inch stroker 460. I gave him the trans bellhousing from my old 78 Country Squire that originally came with a 351M/FMX/integral rear. His FMX has only been rebuilt once in over 30 years he's owned the car! - and that was only because once he took off the starting line with the 484-inch motor with the trans in Second gear. BTW, that car is fully street legal, with full interior, heater, wipers and the works, and weighs 3500# as it sits with the 484, and it runs 11.0s with 60-ft times in the high .130s! There's nothing wrong with a FMX!!!

Many big time racers go to a C-4 automatic over a FMX or C-6 - even behind big blocks - since there is less rotating mass inside the trans, translating into less parasitic horsepower loss through the trans. The guys who run the C-4s have to do some serious modifications to the internals to get them to hold up to severe race duty. Even at that, they will not last as long as a C-6 and need to be rebuilt or refreshed on a more frequent basis. I don't know about you guys, but I don't relish having to drop a trans every couple of years! Me? I'd rather put up with the 'extra' horsepower loss in the name of longevity and run the C-6 my car originally came with.
 

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pic of small case found in most cars of the 60s just before my battery's went dead.
 

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and its bell housing
 

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Thanks for the pictures Ray. I learned something new. Thanks to Tom also.

I agree with Ray, an FMX is OK as long as you can find a shop willing to work on it. No reason to trade an FMX for a C6 or a C4 unless it is beyond repair.
 

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I did not know the AOD was a variation of the FMX so thats got to give some credit to FMXs. We all learned on this one :)
 
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