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Transmission input shaft???

Discussion in 'Flat Fender Tech' started by SandhillMike, Oct 10, 2005.

  1. Oct 10, 2005
    SandhillMike

    SandhillMike Moderator

    Archer, Fla
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    The previous owner of my MB said it had a chevy 350 in it when he bought it, that he took out for another project. The transmission is original. My question is would they have had to change the input shaft to do that 350 swap, or is there a chance that the original go-devil would still bolt up?
     
  2. Oct 10, 2005
    jd7

    jd7 Sponsor

    Nacogdoches,Texas
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    don't you usually use the longer 6 cyl input shaft to do that. Should be able to measure to tell.
     
  3. Oct 10, 2005
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    If original the MB would have a T-84 and to the best of my knowledge there isn't a long input shaft for that. Someone could have retro'd a T-90 in it though in which case with the 350 motor it most likely has the long input shaft. This was real common as the T-84 was VERY weak. Have to know which trans for sure. Nickmil.
     
  4. Oct 10, 2005
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    Mike, David covered the gist of this... I may not be the best person to answer this, but here's what I understand. The MB uses the T-84 transmission. Chevy conversions use the long input shaft from the Willys truck in the T-90 to make the conversion. The T-90 can be substituted for the T-84 in the MB very easily. The Chevy bellhousing is deeper than the L4 bellhousing, so the long input shaft, plus an adpater, is required in order to connect the T-90 to the SBC. I don't know of anyone that's making a T-84-SBC adapter now.

    I believe the input shaft from a T-84 (or a stock t-90) is only about 9" in length. I'd suspect that, if you have the long input shaft and adapter, you actually have a T-90 that's been converted.

    In any case, the only way that the L4 will bolt up is with the stock short input shaft and with a stock bellhousing.
     
  5. Oct 10, 2005
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Hi Timgr,
    I'd never heard you could put a T-90 input into a T-84. That opens up a bunch of possibilities......But not for a JeepR) . Learn new stuff all the time! I'll have to see if I can round up a T-90 input and a T-84 input and compare now that you've got me curious.
    I know you can't use a T-90 input in a T-86 or vice verse without changing all the gears though unless you catastrophic failure. Nickmil.
     
  6. Oct 10, 2005
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    Oh, that's not what I meant. Sorry if I wasn't clear.

    I meant that the complete T-90 can be used in place of the T-84. I have no data re the T-90 input subbing for the T-84 input.
     
  7. Oct 10, 2005
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Oh, Ok! Still got me curious to compare one with the other. Going from memory I thought the T-84 input gear teeth were much smaller, but memory fails me sometimes. That old-timer's disease, and I'm only 36! Guess students will do that to ya.R) Nickmil.
     
  8. Oct 10, 2005
    jd7

    jd7 Sponsor

    Nacogdoches,Texas
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    Now got me curious I was going under the assumption that a T90 was swapped in being that the 84 has a name for weekness with all but stock power. I know that the input shaft is smaller than the T90 but the output is the same, isn't it?
     
  9. Oct 10, 2005
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    The output shaft at the splines for the bull gear is identical from the rear case face to the threads, but the output shaft overall length is definitely shorter. My uncle has a T-84 in pieces at his house. Plan on taking a T-90 input over to compare.....
    Nickmil.
     
  10. Oct 10, 2005
    SandhillMike

    SandhillMike Moderator

    Archer, Fla
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    Thanks a lot guys. I'll have to check the trans more closely. I'll post what I find tomorrow evening.
     
  11. Oct 11, 2005
    SandhillMike

    SandhillMike Moderator

    Archer, Fla
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    OK, on further review, it does appear to be a T90, but the input shaft is only about 8 1/2 inches, measured from the tranny case. While looking at it from underneath I found a notation on the hood that I hadn't seen before that said 1956 265 chevy truck motor, so maybe it wasn't a 350 in it. So anyway, now I'm really confused. The casting # on the tranny is most difficult to read, is there any visual clues to tell a T84 from a T90?
     
  12. Oct 11, 2005
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    You sure that the PO didn't keep the GM adapter and long shaft? The adapter is maybe 4" thick on its own, so your input shaft would only clear it by about 4".
     
  13. Oct 11, 2005
    jd7

    jd7 Sponsor

    Nacogdoches,Texas
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    T84 IIRC is shorter than the T90, noticeably. I think around two or three inches shorter.
     
  14. Oct 11, 2005
    SandhillMike

    SandhillMike Moderator

    Archer, Fla
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    Tim, I dont have the adaptor or bell, just the tranny and T/C. I'm just going on what the PO said, I really have no idea what was actually in it, or when.
     
  15. Oct 11, 2005
    Grandpa Jeep

    Grandpa Jeep Member

    Peyton, CO
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    Yup, T-84 is 6" long and T-90 8" long.
     
  16. Oct 11, 2005
    SandhillMike

    SandhillMike Moderator

    Archer, Fla
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    Measured tranny, 8". So it is a T-90, with an 8 1/2 inch input shaft. Does that mean it will work as is with an original engine?
     
  17. Oct 12, 2005
    Grandpa Jeep

    Grandpa Jeep Member

    Peyton, CO
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    I believe the original shaft stuck out something like 7" so it sounds like you have the longer shaft.
     

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