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Technical how much power can a 39 trans take?

Discussion in 'Traditional Hot Rods' started by JL Kustoms, Feb 24, 2019.

  1. A lot of how much torque a '39 Ford trans will take has to do with how it is driven. If you can drive a stick with no syncros that is half he battle. You can't drive one like you would say a Ford top loader or an M-22 and they are not going to like you missing gears every shift.

    Next you have to decide if he transmission is the weak link in the drive train. IE will you bust a tire loose or break a U joint before you break the transmission.

    In the '50s ands '60s lots of '39 Fords got used behind lots of motors. The really serious guys used the LaSalle transmission instead. But for normal putz around town transmission if you can actually drive a stick the '39 Ford should do just fine.
  2. 1941coupe
    Joined: Jul 4, 2010
    Posts: 402


    IM002510.JPG IM002330.JPG 303 olds 39 top loader 48 ford gears all rebuilt no slop in a 46 merc going on 5 years, drive normal no problem .

    Attached Files:

    don colaps and dan griffin like this.
  3. Ron Plumlee
    Joined: Feb 12, 2012
    Posts: 155

    Ron Plumlee

    Of the 4 I blew in High school, 331 Hemi in a 32 3W, ALL four simply puked the cluster out the bottom of the box.....never had a problem with "second gear" etc as some say they had. Two good buddies had good running 283/301 Chevs, and did drag race them, and had decent luck. So many options these days, why bother with and ancient box unless you are going real traditional.
  4. jimbousman
    Joined: Jul 24, 2008
    Posts: 548


    There is no doubt that with a 39 trans behind a 390 engine, the trans is the weakest link. It may work if you nurse it but it is not a good choice. Even us flathead boys are moving on to a T5 behind our flaties. Better ratios, better reliability, cheaper parts. Might have to up it to a world class behind a 390 but it will work out better down the road.
  5. Bearing Burner
    Joined: Mar 2, 2009
    Posts: 945

    Bearing Burner
    from W. MA

    39 transmission will be fine as long as it is a 39 cad/LaSalle.
    Atwater Mike and jebbesen like this.
  6. tubman
    Joined: May 16, 2007
    Posts: 5,901


    "Even a blind robin gets a worm once in a while".
  7. deathrowdave
    Joined: May 27, 2014
    Posts: 2,743

    from NKy

    I think anything can not be made strong enough that it can not be broken . Old Henry used stuff until it just could not be useful anymore , as stated a stock flathead would break your trans . I would do my best to convert to a top loader with the Jeep top . Just decide if you want 3 or 4 speed . I broke small spline toploaders in my teenage years , they were stacked like cord wood for the junk man. But again your brain is a powerful mechanical object , drive with your brain it will be fun , drive with the brain in bypass , you will have some cord wood stacked up as I did .
  8. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,728

    Atwater Mike

    '68 Torino top loader close ratio 3 speed, Jeep tower with 'big stick'. Real floor shift, relatively short throw...Gears are materialistically wider than my LaSalles!
    This trans is slated for my '54 Ford coupe, behind my new 406 FE I'm now assembling.
    Choice between 3 and 4 speed top loaders? 1/8 mile digs (Eagle Field local) 1 less shift; 4 gears in a short space crowds available time allotted...Think of going thru 3 or 4 gears in a block.
    Besides the 'old-timey' feeling of a 3 speed floor shift in an 'early' Ford... Nostalgia...
  9. F&J
    Joined: Apr 5, 2007
    Posts: 13,222


    dan griffin and banjorear like this.
  10. Newc
    Joined: Mar 25, 2011
    Posts: 208


    Hi all; As soon as the rear tires stick [bite] the trans would break. even with 85 hp. Can you afford this today?? I use a [60's] 3 speed all synco top loader Ford, the big C case... solid trans and cheap. Newc
  11. I just bought my 40 standard tudor and was laying rubber in front of my girlfriend's house on my way home from the purchase. It had a stock '40 flathead and a 39 trans. I laid about 3 inches of rubber before the trans broke.
  12. Yep, I broke two behind a flattie in my 39 Coupe.
  13. jjjmm56
    Joined: Feb 7, 2009
    Posts: 472

    from FL.

  14. hardtimesainit
    Joined: Jan 24, 2009
    Posts: 608


    I agree with most, in that, that 390 IS a lot more than any '39 trans was built for or can hold up against.
    Like one said...put a banger instead and it should hold.
    Ive got zephyrs in couple of my rebuilt '39s, in front of warmed up '32 banger. Has held up well, but then like most say , you need to know how to drive it for its' limitations.
    Just in case though...I keep a like new '42 lincoln side shifter around ...for backup !

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