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T90A vs T90C, What a difference!

Discussion in 'Early CJ5 and CJ6 Tech' started by Brian P, Feb 1, 2009.

  1. Aug 10, 2019
    Rick Whitson

    Rick Whitson Detroit Area 2020 Sponsor 2019 Sponsor

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    Thanks Donny, thought you m[​IMG]ight know. My first Jeep was a 60 Dispatcher.
     
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  2. Sep 14, 2020
    Brian Carothers

    Brian Carothers Member

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    A18F2469-66ED-44F8-81A5-F1FDA5599115.jpeg
    I have a t90c behind my Buick 225? Is that supposed to be like that?
     
  3. Sep 14, 2020
    timgr

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    Why do you think its a T-90C? Appearances would suggest otherwise. I would not go by the shift top casting number, especially since the top and the case have such a different finish.
     
  4. Sep 14, 2020
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2020 Sponsor

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    Replacement for a t86?
     
  5. Sep 14, 2020
    timgr

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    I would guess that a T-90 top might fit a t-86, especially if the T-86 was repaired with T-90 gears.
    A T-90 has a different front pattern from the T-86 or T-14. Look at the side of the case for the cast-in numbers.
     
  6. Sep 14, 2020
    oldtime

    oldtime oldtime

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    Right, the t86aa and t90 shift towers can fully interchange except that they use different 2nd/3rd shift forks.
     
  7. Sep 14, 2020
    Brian Carothers

    Brian Carothers Member

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    so what do I have here fellas?
     
  8. Sep 14, 2020
    oldtime

    oldtime oldtime

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    Open it up so we can see the gears.
    Likely a t90J gearset inside a T86aa case.
    With a late T90c shift tower.
     
  9. Sep 14, 2020
    timgr

    timgr Eppur si muove. 2020 Sponsor 2019 Sponsor

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    I think I can read T-86 on the case. Isn't the Jeep T-86/T-14 adapter iron? Looks like that to me.

    Yes, let's see it from the top with the shifter removed.
     
  10. Sep 14, 2020
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2020 Sponsor

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    Looks like a t86 that has probably had the internals and top replaced with t90 gears. Case does say t86aa...
     
  11. Sep 14, 2020
    oldtime

    oldtime oldtime

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    Yes T86AA is the only case that will fit the 2-5/8” long cast iron adapter and also fit a T90C shift tower.
    The only question is which gear set is inside.
    It’s either T90J or T86AA,
    I’m guessing it’s T90 J because an unmodified T90C shift tower will not fit a T86AA.
     
    Last edited: Sep 14, 2020
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  12. Sep 14, 2020
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2020 Sponsor

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    I defer to old-time....he is most likely correct about the gear set and shifter....
     
  13. Sep 14, 2020
    Keys5a

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    As Oldtime inplies, you likely have a T90J. The "J" is the only long input shaft for use with the adapter, as opposed to the short input shafts used in the "A" or "C" T90's designed for the 4 cyl. engines.
    Remove the six bolts and take a look-see. If the mainshaft has straight splines for the gears, its a T90. If there is a bit of a twist in the splines, you have a T86.
    Also look if there is a tin oil trough up in the front corner of the case by the input gear. If its there, its a T90 A or J. The tin trough doesn't fit in a "C", though it could have been left out.
    Your Tux originally came with a T86 because of the V6. If your Tux would have come with a 4 cyl, you would have had a T90C. The Tuxes a year or two prior to yours came with a column/side-shift T90.
    -Donny
     
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  14. Sep 15, 2020
    garage gnome

    garage gnome Rust polisher

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    Just one observation, why does a 66 with the v6 have a 70/71 clutch cable? Something is not adding up here.
     
  15. Sep 15, 2020
    colojeepguy

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    Someone changed it, evidently. It's got a single bowl master cylinder (to the OP, you really should change that!) so I think it's a '66.
     
  16. Sep 15, 2020
    Fireball

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    Others on the forum have noted Jeep used to sell a clutch cable conversion kit and it was a common repair for a chattering clutch back in the early 70s.
     
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  17. Sep 16, 2020
    Warloch

    Warloch Did you say Flattie??? Staff Member

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    I'm pretty sure its a T90/j top input with T90/a bottom and rear cluster. I tried for several years to find parts to make a T90/c work with a V6... no dice. I eventually sold the T90/c parts (top and bottom clusters) as they are different from the T90/a.
     
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  18. Sep 16, 2020
    Keys5a

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    It takes a shallow bellhousing to mate the T90C to a Buick V6. Stock Buick parts will bolt it up to a Fireball 198. Otherwise, there were aftermarket bellhousings that mated the T90C (or T90A) to both BOP or Chevy blocks.
    -Donny
     
  19. Sep 20, 2020
    Brian Carothers

    Brian Carothers Member

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    I’ll pop the floor back off today and open the top to see the gears. Hopefully we can identify what’s in there. Along with seeing if anything needs repaired.

    what’s the difference between t90 gearing at the t86? One more desirable then the other?

    Also I noticed that back plate on the tranny was removed before, maybe there was a overdrive on there before?
     
  20. Sep 20, 2020
    oldtime

    oldtime oldtime

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    T90J built inside a T86AA case vs T86AA————
    I would say the T90J is slightly superior mainly because of parts availability.
    T86AA parts are few and far between.
    The obvious difference being T86AA gears are helical cut vs T90 gears are mostly straight cut.
     
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