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1939 Ford Transmission question...78 and 48 case numbers...

Discussion in 'The Hokey Ass Message Board' started by 3wLarry, Oct 1, 2012.

  1. 3wLarry
    Joined: Mar 11, 2005
    Posts: 12,804

    3wLarry
    Member Emeritus
    from Owasso, Ok

    I have 2 1939 Ford trannys...one has the number 48-7006 (green one) and the other is number 78-7006 (orange one). They both have the double detent shifter...so what's the difference in them?

    Is one more desireable than the other?...inquirin' minds...
     

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  2. Carter
    Joined: Mar 18, 2006
    Posts: 1,422

    Carter
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    The 78-7006 came out in 1937, I believe. The 48-7006 was 35-6. The only real difference I know of is the size of the bell in front and what clutches will fit it.
     
  3. alchemy
    Joined: Sep 27, 2002
    Posts: 16,575

    alchemy
    ALLIANCE MEMBER

    The 48 case is a 1936 and the 78 case is a 1939. They both work (obviously), but some people say the 78 is better. Don't believe them. The only functional difference is a little extra clearance inside the 78 case for assembling the gears. Once you get the gears in either one, there's no real benefit over the other.

    I put 1939 gears in a 48 case, and all it took was a small bit of fiddling with the cluster and the input shaft on assembly. Mac will hopefully come on next and describe the exact method of installation.
     
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  4. 3wLarry
    Joined: Mar 11, 2005
    Posts: 12,804

    3wLarry
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    from Owasso, Ok

    Because they both have the double detent shifter, does that mean that the shifter has the 3" wide forks?...and are they both synchronized second to third?
     
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  5. Carter
    Joined: Mar 18, 2006
    Posts: 1,422

    Carter
    Member

    Figured I'd just go hunt this down real quick.
    Cut and pasted from Mac Van Pelts website.



    Ford used a similar transmission case from 1932 to 1939 on the passenger cars, and up through 1952 on the light pickup trucks. The early castings were marked 18-7006 (1932-34) and 48-7006 (1935-36). In 1937 Ford introduced the 78-7006 casting. All interchange with previous years, but the 78-7006 case had a slightly enlarged (deeper) bell section to allow for the larger clutch and pressure plates. The 48-7006 case will also handle the 11" clutch, but the 18-7006 will not. The 78 series cases were reputed to be sturdier than previous ones. The shifter housings will interchange on all three cases, as will the clutch release shaft. The Ford parts books will refer to the case by its assembly part number of 7005. This is the bare case and the pressed in bushings for the clutch release shaft.
     
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  6. Carter
    Joined: Mar 18, 2006
    Posts: 1,422

    Carter
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    The shifters can all be swapped from any of the cases. The forks must match the gearset, however.
    Ford went to syncros beginning in 1932
     
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  7. Carter
    Joined: Mar 18, 2006
    Posts: 1,422

    Carter
    Member

    I;m not 100% sure, but I want to say that there are some double detent tops that do not have the 3" fork.
     
  8. 3wLarry
    Joined: Mar 11, 2005
    Posts: 12,804

    3wLarry
    Member Emeritus
    from Owasso, Ok

    I guess I'll have to take the shifters out and check them. I seem to remember that the '39 shifter was 4 7/8" from the ball flat to end of shifter and earlier shifters were 4 1/8"...is that right?
     
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  9. 3wLarry
    Joined: Mar 11, 2005
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    3wLarry
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    from Owasso, Ok

    Thanks Carter.
     
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  10. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
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    Here: http://www.jalopyjournal.com/forum/showthread.php?t=91515&highlight=1939+trans+prices&showall=1

    Early Ford transmissions need to be identified piece by piece if they are altered...anything can be in there. That post covers basic ID of most pieces.
    I don't see any real difference between cases functionally except that pre-1935 (48) cases need minor clearancing for bigger clutch sizes.
    The double detent top will have the late type shifter handle, might or might not have the 3" late fork as they were used with 2 types of gearset.
     
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  11. The double detent shifter came out in '38 and has an 81A- prefix on the part number. The 3" inside width shifter fork came out in '39 with the improved synchro design and has a 91A prefix on the part # which is at the top of the horseshoe. So, double detent shifters can be found with either the early or later style second-high shift fork.
     
  12. 3wLarry
    Joined: Mar 11, 2005
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    3wLarry
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    from Owasso, Ok

    Thanks Bruce...looks like I've got some homework to do.
     
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  13. 3wLarry
    Joined: Mar 11, 2005
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    3wLarry
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    from Owasso, Ok

    Thank you...I'll go out and check part numbers.
     
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  14. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
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    Just slap a ruler across fork...just a hair's breadth under 3" span for late, or look at the synchro...if loose brass rings it is late.
     
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  15. 3wLarry
    Joined: Mar 11, 2005
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    3wLarry
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    from Owasso, Ok

    Ok, The part numbers on both shifter towers is 81 A-7222B...so I don't have the elusive 3" forks.
     
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  16. thunderbirdesq
    Joined: Feb 15, 2006
    Posts: 6,951

    thunderbirdesq
    Member

    You've gotta bust them open and check them out. Like Bruce says, they could be a combination of anything at this point. I've come across a few that had 81a towers with late gears and an added 3" 91a shift fork. I think the top that's in my coupe currently was one of them.

    If the synchro ring has the notch for the fork in the center, that's early stuff, if the notch is offset toward the rear of the ring they're late.
     
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  17. Bruce Lancaster
    Joined: Oct 9, 2001
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    Bruce Lancaster
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    You probably do! The 81A tower was used on all original big fork transmissions as well as on the last small fork ones, so most have the big one. The only 91A part in there is the actual fork, which usually has a TINY part # forged into it. Just pop the top and look for the brass rings. After that, use the article to ID the gears.
     
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  18. Fortyfordguy
    Joined: Sep 16, 2002
    Posts: 643

    Fortyfordguy
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    Looks like you are getting answers from others here. One detail i will add.....we've had two 48 cases thru our shop that had very early 1937 serial numbers stamped into them. If i had to guess, i would venture that Ford used up some leftover 48 cases in their first '37 production runs.

    Don't just trust the 3" width you measure on any old second/high shift fork. It could be a 36-38 type that someone ground the tips to make it fit the 39-50 synchro. The correct fork will have the "91A-7230" cast into the fork near the top of the curve.
     
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  19. 3wLarry
    Joined: Mar 11, 2005
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    3wLarry
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    from Owasso, Ok

    Ok, I'm going out to take the tops off...thanksabunch guys, I'll let you know shortly.
     
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  20. From what I have found, all double detent towers have the 81A cast in em, and the large fork will have 91A-7230. Easiest is remove 6 bolts and 1 second is all it takes to identify it.
     
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  21. 3wLarry
    Joined: Mar 11, 2005
    Posts: 12,804

    3wLarry
    Member Emeritus
    from Owasso, Ok

    Here's the pics from the green trans...#48-7006...it has the 3" forks...yay.

    It also has a number on the bell of 18-3114661

    The bell is 13" in diameter

    I'll have the other pics of the other trans in a minute...
     

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  22. Bruce Lancaster
    Joined: Oct 9, 2001
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    Bruce Lancaster
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    See the brass ring synchro? Instant ID without looking for your glasses so you can see the 3 on the ruler!
    The serial is 1936...so it was born with different gearset and the single detent '36-7 top, which top never had 3" fork but can accept one...unlike the '35 back tops.
     
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  23. 3wLarry
    Joined: Mar 11, 2005
    Posts: 12,804

    3wLarry
    Member Emeritus
    from Owasso, Ok

    Here's the orange trans #78-7006...no 3" forks...boo.

    Bell number is 18-42940633?

    The insides of this one are totally different from the #48 one.

    The bell looks to be 13 1/8" in diameter.
     

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  24. 3wLarry
    Joined: Mar 11, 2005
    Posts: 12,804

    3wLarry
    Member Emeritus
    from Owasso, Ok

    So now what do I do...take the best of both and make one good one? Which parts to use on which one?...inquirin' minds...

    btw...the orange gears look like shit...kinda ruff sounding when you spin it and it doesn't shift well.

    the green one spins nice and shifts nice.
     
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  25. Just sell them as is.
     
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  26. 3wLarry
    Joined: Mar 11, 2005
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    3wLarry
    Member Emeritus
    from Owasso, Ok

    I want to keep the best one to put behind my 283.
     
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  27. awe, In that case I would use the 78 case with the 3 inch fork and gears. I hear they are thicker in the bottom which makes the case less likely to crack when abused....just hearsay though.
     
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  28. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    Serial # is one digit too many (if you just doubled the final 3, 1938)), but the 78 case means '37 or newer and early synchro type means no later than '39.
    Either is OK, but use the one with late synchro, assuming innards look good.
     
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  29. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    Serial # is one digit too many (if you just doubled the final 3, 1938)), but the 78 case means '37 or newer and early synchro type means no later than '39.
    Either is OK, but use the one with late synchro, assuming innards look good.
    (case strength...IMHO, cases do not fail because of the slight differences in strength. They fail from MASSIVE forces like a chipped tooth getting into meshed gears and forcing the shafts away from each other.)
     
    Last edited: Oct 1, 2012
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  30. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
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    If so...Zephyr! Not all LZ have the cutout to aid assembly, but only Zephyrs have the cut. But you can just count the teeth on input on normal early Ford/Lincoln gearsets and subtract that from 44. So 16 teeth up top means 28 tooth cluster, etc.
     
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