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Thread: Mustang Transmission Options

  1. #11
    Senior Member Grass-Passer
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    I bought Marshall's Astro when he parted his car out. So far so good. I also have a WC T-5 and a 12-spline clutch that will be on the trailer for out of town events just in case.

    I had a freshly rebuilt (professionally) T-5 break 3rd at Cresson last year after 5 sessions on track. My theory is that the case bearing bores get out of aligment and we don't check them for alignment before assembly. Then less than adequate tooth contact and boom, broken gears.
    Daniel Records
    CMC # 34

  2. #12
    Modifications need to fit a legal gearbox to a legal engine and make the driveline work are CMC legal...as long as not done so as to gain other advantages. For example, you're likely to need to make modifications to the trans cross member to mount a different gearbox that has the mount two inches farther rearward and that's expected and ok but if those modifications result in the transmission also moving three inches lower then not ok. Logical?
    Al Fernandez

  3. #13
    Senior Member Carroll Shelby
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    Quote Originally Posted by Al Fernandez View Post
    Modifications need to fit a legal gearbox to a legal engine and make the driveline work are CMC legal...as long as not done so as to gain other advantages. For example, you're likely to need to make modifications to the trans cross member to mount a different gearbox that has the mount two inches farther rearward and that's expected and ok but if those modifications result in the transmission also moving three inches lower then not ok. Logical?
    Gear ratios also have to follow the rules.
    Bryan Leinart
    CMC #24

  4. #14
    Senior Member Carroll Shelby RichardP's Avatar
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    Quote Originally Posted by Al Fernandez View Post
    Modifications need to fit a legal gearbox to a legal engine and make the driveline work are CMC legal...as long as not done so as to gain other advantages. For example, you're likely to need to make modifications to the trans cross member to mount a different gearbox that has the mount two inches farther rearward and that's expected and ok but if those modifications result in the transmission also moving three inches lower then not ok. Logical?
    That's all logical but it's not really what we are talking about. The Tremec 3650 transmission has an integral bellhousing. That bellhousing is shaped such that you just can't drill a new bolt pattern to mate it up to a 5.0 pushrod block. To get this transmission to work on that motor, you have to replace the entire front of the transmission with a custom adapter plate that contains and locates all the bearings, shafts, shift rails, etc. in the front of the transmission. You then mount the transmission using a stock T5 bellhousing.

    Making accommodations to mount a legal transmission is different than altering a legal transmission so it can be mounted. If you materially/structurally alter the transmission so you can bolt it up, is it still a legal transmission? It still mounts in the same location with legal gear ratios. I can see both sides. I'm thinking you might get different answers out of different people. I wouldn't want to risk showing up at nationals with something like that...


    Richard P.
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  5. #15
    From what I can tell this 3550 doesn't have the road race 5th gear, might be a problem at COTA. To get it, I'll have to change all the gears in the box I think. I'll probably fix it at some point, but tentatively thinking of going T5 again.

    - J

  6. #16
    Senior Member Grass-Passer Wade's Avatar
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    Stick with the Tremec 3550, 500, or 600. If you can break a TKO, for any reason, you won't make a weekend with a T5. Been there, done that. The cars T5's were designed for had 200 RWHP stock. We push 260 and put them in extreme conditions. That's sillyness and asking to break.
    '86 Mustang Coupe - CMC2 34

  7. #17
    Senior Member Carroll Shelby
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    Quote Originally Posted by Sook View Post
    From what I can tell this 3550 doesn't have the road race 5th gear, might be a problem at COTA. To get it, I'll have to change all the gears in the box I think. I'll probably fix it at some point, but tentatively thinking of going T5 again.

    - J
    If you stick with the 3.27's you shouldn't need the RR 5th.
    Tyler Gardner
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    www.dfwmustangs.net

  8. #18
    Senior Member Carroll Shelby ShadowBolt's Avatar
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    Quote Originally Posted by mach1 View Post
    If you stick with the 3.27's you shouldn't need the RR 5th.
    I had to go to fifth with 3:31's but Kevin was okay in fourth with 3:27's.

    JJ

  9. #19
    Senior Member Carroll Shelby marshall_mosty's Avatar
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    My vote would be an A-5 conversion for the T-5. Best shifting transmission I've owned. Do spend the extra few hundred bucks for the upgraded mainshaft. Facebook reminded me that I broke my stock mainshaft in my A-5 3 years ago at MSR-H... LOL

    Michael drove a 3550 for 10 years before it finally literally wore out. It never "broke" and once he upgraded a few parts on the 5th gear side, it worked flawlessly. His box has a RR 5th gear and I'm sure he would sell it, but according to Joe Dietrichs it needed about $800 worth of "love" to get it back to "new-ish" condition. He's currently using a TKO-600.
    Marshall Mosty
    AI/SI Texas Regional Director
    2011 NASA-TX American Iron Champ
    AI #67 "Mosty Brothers' Racing" (RIP)
    ST6 #21 Toyota Corolla (being revived)...

  10. #20
    Quote Originally Posted by mach1 View Post
    If you stick with the 3.27's you shouldn't need the RR 5th.
    I had to go to fifth with 3:31's but Kevin was okay in fourth with 3:27's.

    JJ
    I thought everyone used 5th on the TWS front straight? COTA's back straight is way longer than TWS front straight.

    - J

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