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Converting my C6 to a toploader

Discussion in '1965-1970 Shelby Mustang GT350 & GT500' started by Oregon Shelby, Nov 29, 2009.

  1. Oregon Shelby

    Oregon Shelby Well-Known Member

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    I have always wanted a 4-speed car and am thinking of converting my C6 to a 4-speed or possibly a 5-speed, but have several questions from those that have possibly converted their cars.

    I indeed have the 428 FE engine and am in the process of deciding which transmission to use for my 68’ Shelby GT500. When looking for a toploader transmission, will a 1968 390 transmission work or does this need to be a 428 tranny? Not looking for numbers matching. Do I need to be concerned about the year of the tranny to fit my 68” engine? Will any 428 Ford transmission be a direct fit for my engine. Again, I am a novice at this. I am also thinking that I might even go with a 5-speed. Would this be advised or not? Trying to find the pros and cons at this point.

    Also need to find foot pedals. Will a 1967 or 1968 pedals work for my car? Will they be a direct fit to my Shelby? My car is not A/C. Does that matter for the pedals? Just want to research some of this before I make some purchases.

    Any advice would be greatly appreciated regarding this possibly tranny swap

    Thanks for the help.

    brian-
     
  2. Coralsnake

    Coralsnake Well-Known Member

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    No, I don't think the 390 toploader will work. You need a toploader with a big input shaft and a big output shaft. The RUG AE or RUG AE2 are CJ Mustang transmissions.

    You can use either a 67 or 68 clutch pedal assembly. They are different, but interchangeable.

    You will also need a flywheel, the correct flywheel bolts, a clutch, a pressure plate, a clutch fork, all of the linkage in the engine bay, a bell housing, a different driveshaft, a shifter. Make sure you find a pedal support with good bushings and one that is correct for a power brake car.

    Here is some of the items you will need:


    http://www.thecoralsnake.com/clutch


    I would recommend a good toploader site, like this:


    http://4speedtoploaders.com/
     
  3. TLEA

    TLEA Well-Known Member

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    Pete, I think he could use the 390 toploader as long as he used the small spline disc/plate throwout bearing. It certainly would not be as strong as the RUG S/AE toploader though
     
  4. 67GT500#2100

    67GT500#2100 Shelby Forums Pit Crew

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    You are right, my brother did this swap in his 68 fastback. Those parts you listed are the only different parts. Clutch linkage, bellhousing etc. are the same. I would recommend a 5 speed since it is not going to be original anyways you may as well get the awesome benefits of an overdrive.

    Here is the kit my brother used.
    http://www.keislerauto.com/vmchk/ford/mustang/classic-mustang/keisler-perfectfit-kits-for-tko-t45rs/1964-1973-mustang-perfectfit-5-speed-kit-tko-600.64-auto/flypage_tabs.html
     
    Last edited: Nov 30, 2009
  5. The Commissioner

    The Commissioner Well-Known Member

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    If the car is a driver, I highly recommend going for the Tremec 5-speed option as that high gear is great for cruising. Did many small blocks with Tremecs mated to 500+hp Roush engines as well as BB 427/428's with the 10 spline gearbox of theirs. They can handle the torque easily. Many of the aftermarket places sell a complete Tremec mounting kit that is easily installed. All the other parts required have been included in other posts.
     
  6. Coralsnake

    Coralsnake Well-Known Member

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    Okay is it too late to change my answer?

    :evo:
     
  7. Oregon Shelby

    Oregon Shelby Well-Known Member

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    Hey great suggestions from all. I have received several private emails relating to their conversions as well. Looks as if I need to do a bit more research. I think that the best suggestion concerning my car would be finding RUG S/AE although a 5-speed would be another option as well. As far as costs go, looks like the RUG S/AE transmissions will be the more economical conversion for me at this time.

    I am really looking forward to this conversion. Can't wait to have a four speed Shelby once I find all the parts and decide to go this route.

    My close friends are also looking forward driving in a 4-speed Shelby as well!

    If you have other suggestions or web sites that you might suggest, please let me know

    thanks again!

    brian
     
  8. cougar

    cougar Well-Known Member

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    The input spline on a 390 is longer and can put a lot of pressure on the thrust bearing as it will shove the crank forward. It can be used with a different bell housing[one from a truck would work], or cut the input shaft.
    Frank
     
  9. jamesroney

    jamesroney Member

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    Actually, the input shaft from the 390 is exactly correct for the FE engine with the 390/428 bell housing. The extra length input shaft is used in the small block, and is commonly sold as a 390 part, because it has the same spline 1-1/16x10 and pilot hub diameter.

    The Big In 1-3/8x10 transmission is only available stock in close ratio. The nice thing about the Big input tranny is that you also get the 31 spline output shaft. There are now gears available to create a Big in/Big out Wide ratio toploader.

    The Tremec TKO is capable of holding up behind the 428. It has a similar countershaft center distance to the toploader. It is available in Close ratio, and wide ratio, with two available overdrives. It can be configured to bolt directly to the FE bell housing, or you can use it with a plate adapter, which will center the shift stick in the shifter hole. The TKO will want to hit your floorpan, so the crossmember is made a little lower.

    I ran a TKO in my Boss 302, and I am putting one in my GT500 now. I am using the plate adapter. I have my RUG-S in storage. email me for pics.
     
  10. cougar

    cougar Well-Known Member

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  11. 6s524

    6s524 Well-Known Member

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  12. 67GT500#2100

    67GT500#2100 Shelby Forums Pit Crew

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    I put the Astroperformance 650 hp t-5 in my 347 powered 66 fastback. I have beaten the crap out of that thing including alot of quarter mile passes with no issues at all. I had blown two FRPP z spec t-5's up before going with the Astroperformance one. It does have a 26 spline input shaft but that just required a different clutch disc.
     
    Last edited: Dec 5, 2009
  13. 67GT500#2100

    67GT500#2100 Shelby Forums Pit Crew

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    That looks pretty cool, any idea on pricing?
     
  14. 6s524

    6s524 Well-Known Member

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    Rumor is $2,300, but who knows until it hits the streets. It's US made, choice of 2:95 or 2:66 (my preference) 1st gear, and seems plenty strong enough. A GForce T5 with the 2:42 1st gearset and all the other bells and whistles is $2,550. I also don't want to be on the bleeding edge of a new trans either, so I'll wait and see...
     
  15. 67GT500#2100

    67GT500#2100 Shelby Forums Pit Crew

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    That is a little cheaper than the Astro one also, if that is the price. Even if it ends up being higher I have always had good luck with McLeod's stuff.
     

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