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Tranny swap questions

Discussion in 'Intermediate CJ-5/6/7/8' started by Lavman, Sep 8, 2005.

  1. Sep 8, 2005
    Lavman

    Lavman Green Mountain Boy

    Mt Holly, Vermont
    Joined:
    Jul 3, 2003
    Messages:
    41
    Currently I have the I6 258 mated with a T14a tranny and a Dana 20 t-case. I would like to swap in a different tranny to achieve a lower gear ratio.

    1. What I am thinking to do is find a T18a which should bolt right up. I am trying to confirm the input and output info for the T18 and the T18a. What I have found is that the T18 has a 1 1/8", 10 spline input shaft and a 1 3/8" 6 spline output shaft. Is the T18a the same for both?

    2. Shall I assume that I will need to shorten at least the rear driveshaft?

    3. Will the output on the t-case end up in the same location as it is now?

    4. What am I not asking that I should know?

    5. Would a T98 be a better choice? (I prefer to avoid the expensive adapter is possible)

    5. Anyone have a T18a for sale or know of someone who does?

    Thanks in advance for the replies!
     
  2. Sep 8, 2005
    coyoterick

    coyoterick 1975 CJ5

    Falcon, Colorado
    Joined:
    Aug 18, 2005
    Messages:
    14
    Your T-14 has a 10-spline output shaft, the T-18 has a 6-spline output shaft. That means the T-18 won't mate up with your transfer case unless you can find the right bull gear for it.
     
  3. Sep 8, 2005
    Lavman

    Lavman Green Mountain Boy

    Mt Holly, Vermont
    Joined:
    Jul 3, 2003
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    According to the info I found at off-road.com, the T14 has a 1 1/8" 10 spline INput shaft and a 1 3/8" 6 spline OUTput shaft mated to the Inline 6 cyl. The V6 has a 1 3/16" 10 spline output.

    I have the I6 258
     
  4. Sep 8, 2005
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
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    Don't consider a T98; no aftermarket support, and T18s are plentiful and cheap.

    Which T-18 are you thinking of? You can use a Ford or Jeep T-18 with some adapting. The only Jeep T-18s that will bolt up came from CJs, and you'll need the bell housing and plate adapter (if any) to use them.

    Re the T-18 and T-18A, that's not a very clear distinction. The T-18s started in Jeep trucks in the mid 60s, and all had the 6.32:1 1st gear. When the CJ transmission was introduced in 1970 (or so), it took the T-18 designation but it had the 4.02:1 close-ratio 1st gear. The truck transmission became the T-18A, retaining the 6.32:1 gear.
     
  5. Sep 8, 2005
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    I think that's wrong - we went through this in another post re the T-14 bull gear and Tera gears. IIRC they are all 10 spline output - there's only one mainshaft ever made for the T-14.

    The input spline count doesn't matter, since you'll need to pick a clutch plate to match the T-18, and change the pilot bushing to match the pilot tip on the input shaft. What does matter is the input shaft stickout. The shortest input shaft is from a Ford T-18. The Ford T-18 front pattern will match a bellhousing from a T-150 or T-176 CJ, and the stickout will be correct. Use a Ford disk and Jeep cover. You can buy an adpater for the back end of the Ford transmission, or you can use the mainshaft and adapter from a Jeep or IH transmission if you drill a few and plug some holes. You can also take a Jeep pickup transmission and use the Ford input shaft with the above bell. You'll have to dirll a hole in the bell to match the front of the Jeep T-18.

    The other alternatives are the T-18s that came in CJs, and they are either scarce (for the '77-79 granny types) or not granny type (from '72-76 models). You'll need the bell and any plate adpaters, plus the right bull gear for your D18 (actually, you'll need the bull gear in any case).
     
  6. Sep 8, 2005
    Lavman

    Lavman Green Mountain Boy

    Mt Holly, Vermont
    Joined:
    Jul 3, 2003
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    Thanks for the responses so far.

    I was thinking the T18a would be sweet b/c of the granny low. Sounds like I'll need to change my bellhousing and obtain a spacer for the front of the tranny to accomodate the stickout of the T18a main shaft? And bull gear?

    What is the gear ratio on the Ford T18? Is it the same as the Jeep (4.02 1st gear)?
     
  7. Sep 8, 2005
    mb82

    mb82 I feel great!

    Charlottesville Va
    Joined:
    Mar 17, 2003
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    2,715
    6.32:1 first
     
  8. Sep 8, 2005
    coyoterick

    coyoterick 1975 CJ5

    Falcon, Colorado
    Joined:
    Aug 18, 2005
    Messages:
    14
    I've seen the same misinformation at several sites - the T14 only had a 10-spline output. I too have the I6 258, it came with a 10-spline T14.

    It was I who just went through all this, when I installed a TeraLow 20 kit
    and found I couldn't use my T14 with it because the T14 is only 10 spline.
     
  9. Sep 8, 2005
    Lavman

    Lavman Green Mountain Boy

    Mt Holly, Vermont
    Joined:
    Jul 3, 2003
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    Hmmmm, according to the off-road.com site:

    Transmission 1st 2nd 3rd 4th 5th Rev
    T-98 6.40 3.09 1.69 1.00 N/A
    T-18 4.02 2.41 1.41 1.00 4.73
    T-18A 6.32 3.09 1.69 1.00 7.44

    Is this stuff wrong too?
     
  10. Sep 8, 2005
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    Sort of incomplete. There were two different flavors of T18 from Jeep, with the different ratios. There are T18s and T18As with a 6.32:1 1st. All the 4.02:1 1st models were called T18, but not all T18s are 4.02:1 1st. However, all T18As have the 6.32:1 1st. Sorry if this is confusing. Read my post above.

    Note this only applies to Jeep, and is to the best of my knowledge.
     
  11. Sep 9, 2005
    Lavman

    Lavman Green Mountain Boy

    Mt Holly, Vermont
    Joined:
    Jul 3, 2003
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    Thanks a lot for all the info. Since I am a novice on trannies inner workings (only had one apart in my lifetime of 33 yrs) what is a bull gear?
     
  12. Sep 9, 2005
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    The gear that goes on the end of the main shaft and meshes with the gears in the transfer case.
     
  13. Sep 9, 2005
    Lavman

    Lavman Green Mountain Boy

    Mt Holly, Vermont
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    Ahhh, thank you!
     
  14. Sep 12, 2005
    Posimoto

    Posimoto Hopeless JEEP Addict

    Minden, Nevada
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    I used a Ford T18 (6.32:1 1st gear) It wasn't that difficult a swap. I used Noak's kit for the tranny (new mainshaft) and T case adapter. Roughly $600 for the kit. You might also try the GM SM420 as it is also easily adapted and actually has a lower 1st gear than the T18 I helped a buddy put one in his '70 CJ, but it is a V6 not the I6 so bellhousing could be an issue. Novak http://www.novak-adapt.com/ and Advance Adapter www.advanceadapters.com both have a lot of info re: these swaps as well as this site.
     
  15. Sep 13, 2005
    JeepManEd

    JeepManEd New Member

    Joined:
    Aug 25, 2005
    Messages:
    20
    Lavaman, Gets a little confusing huh? I say its a good idea to go to the T18, depending on the route you take here is what you'll need

    Stock Jeep route.
    1. Stock tranny out of 76-79 CJ's + Bell housing and bull gear from same.

    Older Jeep CJ's 75 and back

    1. Stock tranny(maybe 4.02 to 1) and adapters + bull gear.

    Build your own

    1. Stock Ford t-18. (any)
    2. Bell housing from 76 up CJ with Ford pattern t-150, t-176, sr4,(most have this pattern)
    3. Output shaft and adapter from,
    a) Novak or Advance
    b) Donner trans, any jeep t-18, scout t-18 (mated type)
    4 Bull gear that works with your t-case. check here

    5. Assemble the Ford t-18 re-drilling the back of the case to accept the adapter and plugging any holes not used that may leak fluid.
    6. Retrofit pilot bushing in outer most part of flywheel to accept the shorter than stock Ford input to t-150 bellhousing. (Ford has one that only has to be machined down on O.D.)
    Good LUck.
     
  16. Sep 13, 2005
    Lavman

    Lavman Green Mountain Boy

    Mt Holly, Vermont
    Joined:
    Jul 3, 2003
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    WOW! Thanks a lot for all the help. You guys are a great resource!

    Now to Ebay a kidney.................:)
     
  17. Sep 21, 2005
    Lavman

    Lavman Green Mountain Boy

    Mt Holly, Vermont
    Joined:
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  18. Sep 21, 2005
    lynn

    lynn Time machine / Early CJ5 HR Rep Staff Member

    Huntingdon PA
    Joined:
    Sep 20, 2002
    Messages:
    3,449
    Here is a reliable source for parts, kits and information:
    http://www.partsmikeparts.com/t18.htm

    Not cheap, but Mike is a great source of information and parts.
    He can put a package together for you that will be ready to bolt in when you get it.
    Best to deal with him by phone.

    Mike is an AA dealer, his AA prices are often better than dealing direct with AA.

    HTH
     
  19. Sep 21, 2005
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
    Messages:
    11,510
    Don't care what you found on off-road.com. All T-14 four wheel drive Jeep tranny's have 10 spline outputs. I've rebuilt tons of those things. Pretty much all other Jeep tranny using the 18 or 20 transfer case use a 6 spline output. off-road.com is a decent resource but there are some mistakes like that which they refuse to fix even after they admit the info is incorrect so don't take it for gospel without double checking. Not trying to bash/downgrade or anything here, just want to make sure you have correct info.

    Another source for the adapter and shaft is R&P 4 WD Parts Inc. They sell a machined STEEL adapter instead of aluminum for the adapter and can help with tons of info, acquiring the bull gear, they stock the pilot bushing you need, etc. There # is 503-557-8911. Best to call them on the phone. They also sell complete T-18's ready to rock already adapted, or will sell parts. Last time I was up there they also had a couple of the stock '77-'79 CJ T-18's. Nickmil.
     
  20. Sep 22, 2005
    Lavman

    Lavman Green Mountain Boy

    Mt Holly, Vermont
    Joined:
    Jul 3, 2003
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    Thanks folks! I appreciate the info, I am getting more educated by the day! :)
     

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