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Technical C-4 or C-6?

Discussion in 'The Hokey Ass Message Board' started by olskool34, Sep 21, 2016.

  1. olskool34
    Joined: Jun 28, 2006
    Posts: 2,463

    olskool34
    Member

    I am going to run a 302 in my 53 F-100 and was looking at finding a C-4 to back it up. Locally on Craigslist a C-6 has popped up with the small block bolt pattern. Guy says there are about 2k on the rebuild. Any drawbacks about using the bigger trans? Any problems with fit? I don't actually know how much bigger they are than the C-4. He is asking 400 for it.
     
  2. C6 IS physically bigger tan the C4 in all dimensions, but ore important to your 302, they take a Lot more power to run. If I remember right, the C6 is about 30-40 lbs heavier and takes about 10-15% of your power away compared to a C4.
     
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  3. 73RR
    Joined: Jan 29, 2007
    Posts: 6,625

    73RR
    Member

    hotroddon is spot on.
    If you were building a truck for some actual hauling chores then the C6 might be better.
    Save some HP, use the C4.

    .
     
  4. squirrel
    Joined: Sep 23, 2004
    Posts: 49,830

    squirrel
    Member

    Ford never put a C4 in a truck, did they? kind of a wimpy little trans. I'd go C6 for sure. but I'm weird.

    they did put the C6 in the trucks behind the six cylinder, does that tell you anything?
     
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  5. flatheadpete
    Joined: Oct 29, 2003
    Posts: 10,211

    flatheadpete
    Member
    from Burton, MI

    I run a C4 behind my 302 in my '50 Ford CAR.....seems to work well but it's a basically stock '69 302. Feel free to hit me up if you want to take it for a spin.....
     
  6. Crusty Nut
    Joined: Aug 3, 2005
    Posts: 1,834

    Crusty Nut
    Member

    The c6 takes a lot of power to run. Some sources claim about 50 hp. They are also pretty big, but under a truck shouldn't be a problem. Have you considered an AOD?


    Sent from my iPhone using The H.A.M.B. mobile app
     
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  7. Make sure you're aware of the 28 vs 50 ounce issue. 302 Fords are externally balanced and depending on the year could be either balance factor. The wrong flexplate will result in terrible vibration...
     
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  8. squirrel
    Joined: Sep 23, 2004
    Posts: 49,830

    squirrel
    Member

    folks say the same thing about the TH400 taking a lot of power to run. but they don't seem to realize that it's a percentage, not a fixed HP number. I have a C6 in my OT ford pickup, it will creep forward in gear at idle, I kind of doubt it's using 50 hp to do that.
     
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  9. Ford put the C4 in F series trucks from 1965-1983 - mainly the 240" six and 302 powered trucks. No need for a C6 with a 302. the C6 was used behind the 300" six and 351 and larger V8's
     
  10. Dino 64
    Joined: Jul 13, 2012
    Posts: 2,097

    Dino 64
    Member
    from Virginia

    I had a C4 behind a warmed up 289. I think it's only advantage is the small size. The AOD is bigger than a C6 I think.


    Sent from my iPhone using The H.A.M.B. mobile app
     
  11. 69thumper
    Joined: Apr 11, 2013
    Posts: 13

    69thumper
    Member

    a c-6 trans will use 65 horse power. thats a lot to loose from a small block ford. c-4 will work just fine. c-4's are cheap to build too.
     
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 49,830

    squirrel
    Member

    just curious, where did you get that 65 hp number from?
     
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  13. Check and see what rear end gears you got. If they 4.11 you may want to consider the AOD. I put one in my 65 Mustang when the C4 went out and love it. Just be sure to get the correct flywheel.
     
  14. I run a c4 in my 55 F-100. No trouble at all. Went with a Mustang rear for the disc brakes, and it couldnt have worked out better. My driveshaft came out of a 4 door Crown Vic Police car, so it's aluminum, strong, and very light weight.
     
  15. deucemac
    Joined: Aug 31, 2008
    Posts: 1,156

    deucemac
    Member

    C4 's are god transmissions that can be built very simply to take lots of horsepower. From what I remember from Ford school, a C6 takes around 40 hpop and a C4 twenty or so to operate. Put a 4 clutch forward and a 5 clutch direct in it , halve the band adjustment and you will love it. A C6 is bigger in every respect and if it were me, I would save it for big block applications. I have been making my living from Fords since 1962 until I retired and both the C4 and C6 are solid Simpson design transmissions. Either one will serve you well but one weighs lots more and costs you twice the hp than a small block doesn't need to pull.
     
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  16. saltflats
    Joined: Aug 14, 2007
    Posts: 10,932

    saltflats
    Member
    from Missouri

    Sounds like if you can get a C6 for cheep to fit a 302 you better get it and if you don't use it then it will be good trading stuff.
     
  17. Judd
    Joined: Feb 26, 2003
    Posts: 1,894

    Judd
    Member

    Two guys down here replaced the c6 in their 427 Fairlanes and got almost .5 seconds in the quarter mile from weight loss of trans and rotating parts. They eat power.
     
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  18. Bearing Burner
    Joined: Mar 2, 2009
    Posts: 937

    Bearing Burner
    Member
    from W. MA

    C4s from 4&6 cyl cars have fewer clutches which cannot be increases as opposed to those from 8 cyl vehicles which can.
     
  19. Sounds like the same Ford School I went too.
     
  20. squirrel
    Joined: Sep 23, 2004
    Posts: 49,830

    squirrel
    Member

    That's amazing!

    I wonder what the rest of the story is? Did the torque converter change? How much power is the engine making, compared to a mild 302? How much did the mph change?

    my guess is that the C6 was not set up to work as best it could, and the C4 was. I also wonder what the cost difference was between the two setups. And how long the C4 would last in a street/strip application. And also, what this has to do with a transmission for a truck.
     
  21. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    I think its probably somewhat exaggerated but even modified C-6's are real power hogs. I have heard more like .25 to .3. I ran one with needle bearings and a T/A valve body behind my 428, and when that engine goes back together, it will be with a C-4, big investment because nothing will switch over from the C-6.
     
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 49,830

    squirrel
    Member

    If you're going class racing, and it's allowed, sounds like the C4 would be a worthwhile swap.

    Otherwise, I don't get it.
     
  23. 73RR
    Joined: Jan 29, 2007
    Posts: 6,625

    73RR
    Member

    For the OP's project, a C4 is a good choice simply due to the 'likely' usage and the weight of the truck which is usually around 3200 lbs in 'stock-ish' configuration. The C6 will certainly do the job but there are 'hidden' costs attached.
    Yes, there are some variations with the C4 so attention to details is important.

    .
     
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  24. olskool34
    Joined: Jun 28, 2006
    Posts: 2,463

    olskool34
    Member

    My rear gear is a 3:50, ford 9 inch. I passed on the C-6. Looking for a C-4 now. There is a guy close that has a rebuilt FMX trans, not familiar with those. Is it a good candidate or should I keep looking for the C-4?
     
  25. bchctybob
    Joined: Sep 18, 2011
    Posts: 3,256

    bchctybob
    ALLIANCE MEMBER

    I've got a '55 F100 with a 302 and a C4 and it works fine for everyday stuff. The first 302/C4 combo I had in it was from a van. The motor developed a knock so I horse traded for the 302/C4 combo that I'm currently running. The van transmission was definitely stronger than the current one (C4 from a '65 Mustang)- tighter, crisper shifts, quicker reacting when you move the shift lever.
    I'm no Ford expert, but it may be that the truck/van versions of the C4 are a little more heavy duty than the passenger car versions. If you don't have a trans and are looking for one, I would lean towards the truck version over the little Mustang/Falcon version. The only reason I went with the passenger car trans was because someone had done some questionable mods on the tail shaft housing and they welded up the speedo hole.
    I'm sure the Ford guys can confirm or deny this observation.
     
  26. I would pass on the FMX tranny, they are heavy cast iron units, just about the same as the old Cruise-o-matics
     
  27. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    If you are going to do a C-4, you want either a '71-up V-8 C-4, or a '82-up C-5. Other cores can be used, but the complication factor rises, starting in '71, they had the 26/24 spline .839" input shaft, all your off-the-shelf aftermarket converters are designed around the '71-up input shaft, so earlier trans you either need a custom converter, or you have to swap in the later input shaft/front drum combo.
    Pre-'67 used the so-called "Green dot" valve body, so now you need to swap the valve body as well as the input shaft/front drum. Its all do-able, but to keep it simple, stick to '71-up cores.
    I have had a small-block C-6 core here I have been trying to sell for a while, no-one seems to want the goddam thing.:rolleyes:
     
  28. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    three tenths is 30+ horsepower. The current re-vamp I am doing on my FE should come in around 725hp naturally aspirated. How much do you think it would cost to gain another 30hp at that power level? And after that, you STILL have 3 tenths left in the trans. It just doesn't make sense to run a C-6 in anything that will see track time.
    And the C-4 has WAY more aftermarket support than the C-6, which has very little. Even chevy powered Comp Elim. guys are using C-4s now, the aftermarket support for them is huge.
    In the nineties, NHRA Stock eliminator FE racers were filling their C-6 cases with 904 Mopar internals, crossbreeding from different makes was illegal at the time, I was at the Boise WDRS when Richard Pauley re-set the D/SA record in his Torino, and got bounced in teardown for this. This happened on Saturday, that night, every motel parking lot in town rang with the sound of C-6s coming out from under 428CJ stock elim cars, to be replaced by legal transmissions.:eek::D
    Shit like this is why I always LOVED Stock eliminator. The real entertainment was always behind the scenes.;)
    As far as using a C-6 in a truck where performance has no bearing on the issue, I would say its a toss-up. In near stock form, the C-6 is stronger than a near stock C-4, not much. If you had a small-block C-6 sitting there, I would say use it. Otherwise, I would hunt up a '82-up C-5, which is a slightly beefed C-4. All three cores will cost about the same, so may as well find a C-5. The C-5 case has improved hydraulic circuitry as compared to the C-4, and the case is a little beefier.
    I would think hard about an AOD as well.
     
    Last edited: Sep 22, 2016
  29. About 15 years ago I replaced the cruise-o-matic "green dot" in my 66 Galaxie hardtop after the warmed up 390 I build for it toadsted the trans. I got a core from a mid 70's 2WD pickup, and I had a local guy rebuild it. He put a shift kit in it. Cost me $350.00 not including a torque converter because I wanted a stall...I think that was another 2-300? That trans shifted so smooth and quick! I couldn't imagine spending $2,000.00 on an old 3 speed auto in stock form!
     
  30. squirrel
    Joined: Sep 23, 2004
    Posts: 49,830

    squirrel
    Member

    george-good to see we agree on this :)

    Either one will work, assuming it's in good condition. I tend to like the bigger transmissions, because they are designed to handle the load of a heavier vehicle, and larger engines, by design. The smaller transmissions usually need some help to keep up. But then, I'm a lazy cheapskate.

    Whatever you can find that fits, and that you can freshen up for a reasonable price, would be the way to go.

    I don't know why folks think race car parts are what they want in their cruiser pickup truck. It boggles the mind.
     
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