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T90 To T18 Swap

Discussion in 'Early CJ5 and CJ6 Tech' started by colojeepguy, Aug 5, 2022.

  1. Aug 17, 2022
    Norcal69

    Norcal69 Out of the box thinker 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Northern California
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    Your probably correct when considering that he only has 2.5" lift and short shackles.
    All in total my jeep is probably in the 4"-4.5" lift range between aftermarket hangers, springs and shackles.
     
  2. Aug 17, 2022
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
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    Sure. Here's some photos from the archives.

    ITLKSEZ came down to help me modify the crossframe and get the transmission/trasfercase bolted in. With his help, it took an afternoon instead of the 3-4 days it would have taken me alone. I'm slow.

    We ended up putting a saddle in the crossframe since the T-18 mount is overall taller. We placed the mount in the middle of the crossframe front-to-back, we needed to heat and pound the crap out of the indents on the right side of the crossframe for enough transfercase clearance. Modifying the original crossframe saved a lot of time vs fabbing a new one.

    The final product:
    [​IMG]

    Amazingly, it lined up with existing holes in the bottom of the frame. You can see how much further back it is from the original location:
    [​IMG]

    The mount Novak recommends for their adapter is a GM 2268 unit. I found an NOS Borg Warner one on ebay figuring it would be better quality than anything new. Not sure if your Jeep adapter uses the same mount.

    The spacer under the mount was to gain a little more clearance to the transfercase drop on the right side of the crossframe:
    [​IMG]

    For torque reaction mount, I drilled out a body mount rivet and used it's hole and another existing hole that lined up perfectly:
    [​IMG]

    The indent in the back of the mount is like it's made to clear the remaining rivet head:
    [​IMG]

    For the clutch cable, I thought I would get super clever and make an offset mount that kept the end of the cable in the same place:
    [​IMG]

    But the stackup of the new clutch, pressure plate, and throwout bearing was different than the original clutch and the cable wouldn't reach. I made a"temporary" extender by threading some tubing while I waited for some 5/16-24 coupler nuts and threaded rod to show up:
    [​IMG]

    The coupler nuts and rods have shown up but my "temporary extender" is still there and working great. If I started over, I would not have wasted time modifying the bracket and just made a longer extender.
    [​IMG]
     
    melvinm, Fresbone, ITLKSEZ and 4 others like this.
  3. Aug 17, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Hey Doug (and Roy and all) - i only have a sort of armchair understanding of the T18 swap, but was thinking about the OAL of the T18 and how much does it really push things reward. I realize Doug currently has a T90 in his cj, but it would have been a T14 originally. Doug - is all of your cross-member and driveshafts in their original T14 locations? If not, maybe this discussion doesn't relate.

    Basically, where I am going with this....The T14 has a 8.75" case length, which sits behind the 3" bellhousing adapter (in an OEM configuration) - so total length between bellhousing and D18 is 11.75". With a T18 - assuming you mount directly to the BOP bellhousing, the case length is just under 12", and I assume a 1" D18 adapter, so that is just under 13" total.....so the swap should push the D18 back just under 1.25".

    In the case of the rear driveshaft, it makes it shorter, but is it enough to warrant new rear driveshaft - I recognize it won't be exactly 1.25" shorter given the triangulation, but for reasonably low driveshaft angles its pretty close? Plus, I might argue that when the 2.5" lift kit was installed - that lift kit initially lengthened the distance between the D18 and rear diff, albeit somewhat minor (a little trig suggests maybe something in the 1/2" range?). So, I am guessing your driveshaft length will not even be one inch shorter than the OEM configuration. As for the front driveshaft, in this case, both the lift and and the rearward push of the D18 lengthen the driveshaft - so that might get closer to 2"? I also understand there is some benefit to replacing the small diameter/ujoint front driveshaft regardless of length concern, as well as maybe its just time to refresh/replace 50 year old driveshafts. Anyway, just wondering how much driveshaft length change is really going to happen, and if that truly necessitates modifications.
     
  4. Aug 17, 2022
    colojeepguy

    colojeepguy Colorado Springs

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    T90 with adapter is 10 5/8"
    T18 with adapter is 13 1/2"
    So I'm going to be moving the tcase rearward 2 7/8".
     
  5. Aug 17, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    So it sounds like things were further forward with the t90j than with a T14?
     
  6. Aug 17, 2022
    colojeepguy

    colojeepguy Colorado Springs

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    Not sure...the only T14 I have is under the Commando! My dad swiped the original T14 out of my CJ to put in his Jeep....that was 23 years ago and I don't remember exactly what I did to put the T90 in it.
     
  7. Aug 17, 2022
    oldtime

    oldtime oldtime

    St. Charles,...
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    BORG WARNER
    T90 case = 8”
    T90 J adapter plate to GM= 2-5/8”
    T86AA case = 8”
    T86AA adapter plate to GM= 2-5/8”
    T14 = 8-3/8”
    T14 adapter plate to GM = 2-5/8”
    T15= 10”
    T15 adapter plate to GM = 1-5/8”
    T98 = 11-7/8”
    T98 front adapter plate to Willys 134 = 7/8”
    T98 rear adapter plate to D18/20 = 1”
    T 18 = 11-7/8”
    T18 front adapter plate to ? = ? (never had one)
    T18 rear adapter plate to D18 /20 = 1”
     
    Last edited: Aug 17, 2022
    OldAdobe and timsresort like this.
  8. Aug 17, 2022
    colojeepguy

    colojeepguy Colorado Springs

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    The T18 to GM adapter I have is made by AA and is exactly 1/2" thick.
     
  9. Aug 17, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    I saw that researching their site....don't know if 1/2" is worth saving the length, but you can pretty easily rework the BOP bell to accept the ford T18 and skip the front adapter. My calculations assume no front T18 adapter - just a rear adapter. The Jeep T18/D18 adapter is 1" - wasn't sure what the AA or Novak T18/D18 adapter thickness is.
     
    Last edited: Aug 17, 2022
  10. Aug 17, 2022
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
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    Your setup will be 1/2" longer than mine. I did the GM bellhousing mounted directly to a Ford T-18 thing James is mentioning. The one thing I didn't like about that was Novak wants you to drill through this unused tab and tap the bellhousing:
    [​IMG]

    But the there is no cast-in boss in that part of the bellhousing:
    [​IMG]

    The engineer in me didn't like that. I made a bridge that spanned the ears on the transmission and picked up the original bolt hole on the bellhousing:
    [​IMG]

    The Novak adapter is also 1" thick.
     
  11. Aug 17, 2022
    colojeepguy

    colojeepguy Colorado Springs

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    My T18 is out of a Jeep pickup, no Ford involved.
     
  12. Aug 17, 2022
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    The T-14 adapter is 2 5/8". The Ford T-18 to GM bellhousing and D18 adapter ends up about 1.5" longer overall than the stock T-14 setup.

    Note the factory slip joint in the drive shafts only has about 1 1/4" of travel.

    All the way in (seal collar tapped off for visualization):
    [​IMG]

    Out to where the seal collar would stop it:
    [​IMG]

    You only have a 5/8" margin each way from the center of travel. You definitely need match the length when you move the transfercase 1.5" back.

    Now if you have a Tom Woods driveshaft with 4.5" of slip yoke travel you could do it. In fact the new Tom Woods front shaft in my '71 is intentionally 3/4" short because I'm planning on a Front 44 eventually.
     
    Jw60 likes this.
  13. Aug 17, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    the reference to ford T18s in this case is more about the ford butterfly mount pattern which jeep also used on T18s in later years....don't know the details about FSJ T18s, and when they might have used the earlier jeep T18 asymmetrical bolt pattern (like on 72-76 cj) vs the ford butterfly....besides, once you put the short ford style input shaft in it, there ain't much difference except maybe the PTO port
     
    Last edited: Aug 17, 2022
  14. Aug 17, 2022
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Yeah, I know. I posted that mostly for James' benefit.

    The Ford T-18 does have the advantage of being 1/2" shorter with out the need for a front adapter and the clutch splines/pilot bushing probably engage better.

    Disadvantages are grinding needed on the back of the transmission for the reversed transfer case bolt, possibly grinding to clear the dual stick tower, and the PTO port being useless on the passenger side of the case since it points right at the front drivline.
     
  15. Aug 17, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    hmmm....I take mine on and off quite a lot when I am flat towing....I seem to have more like 3+" of travel....makes me wonder the history of my driveshaft.
     
  16. Aug 18, 2022
    oldtime

    oldtime oldtime

    St. Charles,...
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    I much prefer to adapt the Jeep T18 case to a dauntless and don’t use a front adapter plate.
    OAL is 12-7/8”.
    I use nickel rod to arc weld ears onto the front of the case to match up with the BOP bellhousing.
    My T18 looks like it’s made for a GM bell.
    Oh …. Because it is !
    And the PTO remains available, just in case.
    Got the T18 fit into my flatfender and every little bit helps.
    [​IMG]
    [​IMG]
     
    Last edited: Aug 18, 2022
    Fireball, Twin2 and colojeepguy like this.
  17. Aug 18, 2022
    Jw60

    Jw60 Cool school 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Is the seal collar not supposed to be splined?
    I suppose mine could have self clearance on the rear, my Jeep is on it's 3rd front driveshaft but they all have more than 2" travel when out of the vehicle.
     
    Fireball likes this.
  18. Aug 18, 2022
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Good point. But even at 2" pulled out, you would only have a little over an inch of spline engagement which seems less than ideal. And even with 2" of travel, you would still need to adjust the driveshaft length since you only have +- one inch from center.
     
  19. Aug 18, 2022
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
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    Both of my T18 installs used new cases I got from R&P with the front setup to bolt to the stock bell. While it moved things back a touch, it really didn't concern me with my plans. I also put 2.5" lifts on (roughly) and new long extension shafts from Tom Woods. A bit more than having them remade here in town, but the long stroke makes a lot of things much easier IMOP.

    Your putting about a grand into a swap - don't skimp on the important things IMOP. Its always come back to bite me in the A$$ in the long run when I did.

    I fabbed new cradles and mounts for my setups too. Didn't even try to adapt stock crossmembers.
     
    Fireball likes this.
  20. Aug 18, 2022
    colojeepguy

    colojeepguy Colorado Springs

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    I'm hoping to do something similar to what Fireball posted above...not all of us have your fabrication skilz!!
     
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