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T90A versus T90C

Discussion in 'Early CJ5 and CJ6 Tech' started by linckeil, Nov 3, 2004.

  1. Nov 3, 2004
    linckeil

    linckeil Member

    Danbury CT
    Joined:
    Aug 19, 2004
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    492
    The topic of the differences between these two transmissions came up a couple days ago in a thread here....
    http://www.earlycj5.com/forums/showthread.php?t=8058

    I have a quick follow-up.

    My '60 (which should have come with a T90A per the Novak site) does in fact have the 18 tooth input gear, meaning it is a T90A. The case is also marked T90A, and the shifter cover is simply marked T90.

    My '64 (which should have the T90C per the Novak site) also has an 18 tooth input gear, meaning it is a T90A, and not a T90C. The case is marked T90A and the shifter cover is marked T90C.

    I am making this post for 2 reasons. One, for confirmation that both my transmissions are T90A's, despite their markings (and because they are T90A's, they are both able to accept the longer input shaft which a T90C cannot). And 2, to let people know that only way to tell what you got despite the year jeep and the markings on the transmission, is to pull the cover off and count the teeth on the input gear. (T90A=18 teeth. T90C=16 teeth)
     
    linckeil, Nov 3, 2004
    #1
  2. Nov 3, 2004
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Sep 23, 2002
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    12,529
    Dead on! Same thing I tell people when they try to identify their trans gear ratio's by markings on the case. You HAVE to look inside and count teeth to positively identify specifically which tranny first gear ratio you have! Too many changes could have been made over the years! That's why when you call a tranny supply house they don't care what year the tranny is, they want gear tooth counts, then worry about year of the transmission.:( Nickmil.
     
    nickmil, Nov 3, 2004
    #2
  3. Nov 3, 2004
    Hawk62cj5

    Hawk62cj5 Captain of OldSchool

    Brodnax Va.
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    Oct 28, 2004
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    694
    thanks for the tips man :beer: Im new to the jeep world so any thing like this is a great help.
     
    Hawk62cj5, Nov 3, 2004
    #3
  4. Nov 3, 2004
    DanStew

    DanStew Preowned Merkin salesman Staff Member

    Lexington, South...
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    Sep 22, 2002
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    Actually my T90C has the long input shaft on it.
     
    DanStew, Nov 3, 2004
    #4
  5. Nov 3, 2004
    linckeil

    linckeil Member

    Danbury CT
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    Aug 19, 2004
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    DanStew,
    Was the input gear swapped out from a 16 tooth model to a 18 tooth model?
     
    linckeil, Nov 3, 2004
    #5
  6. Nov 3, 2004
    DanStew

    DanStew Preowned Merkin salesman Staff Member

    Lexington, South...
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    To tell you the truth i didnt do the swap. I can go out later and count the teeth, i do have it sitting on the floor
     
    DanStew, Nov 3, 2004
    #6
  7. Nov 3, 2004
    linckeil

    linckeil Member

    Danbury CT
    Joined:
    Aug 19, 2004
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    492
    Well if you have the 18 tooth gear in there, then what was a T90C was effectively changed into a T90A. And that would make sense to me.
    If it is the 16 tooth gear, it is still a T90C and I would be surprised to hear someone made a long input shaft work with the 16 tooth gear of a T90C.
    Let us know.
     
    linckeil, Nov 3, 2004
    #7
  8. Nov 3, 2004
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
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    Mar 4, 2003
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    FWIW - I have seen a custom input shaft made by crossing the cluster from a C with the shaft on an A... That was 30 years ago, and Mr C (as we knew him) was the only one I know with one.
     
    Warloch, Nov 3, 2004
    #8
  9. Nov 3, 2004
    DanStew

    DanStew Preowned Merkin salesman Staff Member

    Lexington, South...
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    Wasnt the T90C available in the wagons and trucks??
     
    DanStew, Nov 3, 2004
    #9
  10. Nov 3, 2004
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    I'm confused here. If the input shaft ratio changed that would change all gear ratios except for 3rd, which is direct of course. I thought the deal was that 1st gear was changed to a lower ratio to compensate for 4.27's becoming standard. I thought this was accomplished with a different cluster gear/1st gear combo, and I guess a different reverse idler gear?
     
    Glenn, Nov 3, 2004
    #10
  11. Nov 3, 2004
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
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    Glen - you are correct - the C has a different input, and lower cluster to get the lower first gear.
     
    Warloch, Nov 3, 2004
    #11
  12. Nov 3, 2004
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
    Joined:
    Jul 30, 2003
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    8,525
    For T90C the tooth counts were:
    Main drive gear: 16-30 teeth
    Cluster: 35-26-19-14
    For T90A, the tooth counts were:
    main drive gear: 18-30 teeth
    Cluster: 33-26-19-14
    these were short shaft 4 cyl applications only
    FYI
     
    jpflat2a, Nov 3, 2004
    #12
  13. Nov 4, 2004
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    Ok, as I read it only the input shaft and the corresponding gear on the cluster are different. So I was backwards on my thinking there. So is Warloch saying my thinking all gears except drive would have a different ratio is correct? Also I assume accidently using a mismatched input/cluster gear couldn't work. Seems like something would break quickly. :?
     
    Glenn, Nov 4, 2004
    #13
  14. Nov 4, 2004
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
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    Glen go to Novak T-90 as it is broken down real well there. As a Summary, First and Second have different gear ratios. This is a result of the different lower cluster (the bottom row of gears in the Tranny). I never took the time to count the teeth on the 2nd gear top and see if it's different from an A to C. It is possible to have a slightly different tooth count on the bottom row and by changing the gear size (diameter of the gear it self) change the ratio without changing the 2nd gear on the top row. I do not know if that is the case as I really stopped looking at it when I found I could not get a C to work with a V6.

    And to your last question - NO you can not get a miss matched input and bottom row to work together - BIG BOOM - :rofl:

    Let me know if your still confused - a complicated subject, but really worth understanding if your customizing things.
     
    Warloch, Nov 4, 2004
    #14
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