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More T18 Discussion...

Discussion in 'Early CJ5 and CJ6 Tech' started by FinoCJ, Sep 20, 2022.

  1. Sep 20, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Bozeman, MT
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    Starting point is 72-75 jeep cj 4:1 T18 - so it has 23t input shaft gear, and a stickout of about 9.5"....While that is not super long like many of the FSJ input shafts, its not as short as the 17 tooth 'short' ford input shaft often used when swapping in a ford t-18 - I believe the short ford input has a stickout of just under 7" or so. Although the difference in length between the 23t cj input shaft and the short 17t ford shaft is only 2.5-3", that is very significant with regard to the swb of early cj5s. I recognize that you cannot mix a 17t input shaft with the rest of a 4:1 (23t) set of gears. So a couple thought points:

    1) In an ideal world, there would be a shorter 23t input shaft that I could swap in place of the original cj 4:1 23t jeep input shaft. Most research from places like Novak and AA etc say there is no option to swap out a 23t shaft.....an yet what is this:
    https://www.advanceadapters.com/4622
    It says its a 23t T18 input shaft and 9 1/8 OAL - so to me that would mean a stick out of around 6.75" if you assume the OAL is about 2.5" longer than the stickout. Is this real? and if so, would this be the ideal input shaft for for use of a 4:1 T18 in an early cj with BOP bell? I think so....

    2) Some of this got me thinking that if there is no shorter 23t input shaft available, how functional would a cj 4:1 T18 be in an early cj5 with regard to driveshaft length. Back of the envelope numbers suggest the jeep T18 (plus the OEM D18 adapter) is about 4" longer than the current T14....The T14 and the 4:1 T18 have about the same stickout around 9" (if anything, the T18 is longer stickout), so the additional 4" of length cannot be offset with a shorter front end at the bell like with the short ford input shaft T18. With the short ford input, almost 3 inches of length are saved in the front at the bell, thus even with the longer OAL, the rear output of the D18 is only 1-2" further rearward depending on the D18 adapter.

    Basically, shortening the rear driveshaft by 4" seems like it might be a bad idea, and if the above short 23t input shaft doesn't really exist, I might should think about a different way to get a 4-speed installed. Maybe I should swap the sm465 from the 58 into the cj and use this 4:1 T18 in the 58....in many ways, that would be a better match of gear ratios and driveability (and I might even be able to fit my foot on the gas pedal!)
     
    Last edited: Sep 20, 2022
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  2. Sep 20, 2022
    oldtime

    oldtime oldtime

    St. Charles,...
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    Both the T18 and T98 stickout lengths are always 2-5/8” less than the OAL of the main drive gear.
    The 6-1/2” Ford stick out is technically too short.
    Ideal stickout for BOP is 6-3/4” to 6-7/8” stickout.
    For WR T18 I like to use the the 1977-1978 Jeep at 10” OAL then I cut 1/2” off from the extra long input tip.
    So I end up with 6-7/8” stickout.
     
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  3. Sep 20, 2022
    nickmil

    nickmil In mothballs.

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    If you can find one a Ford T-19 23 tooth input can be used in a T-18 if you use a matching 3/4 synchronizer assembly, 3rd gear, blocking rings, and input bearing. Many late Ford T-18’s had the correct parts to do this. Been there, done that for customers on request. Works quite well if you don’t need the 6.32-1 first gear.
     
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  4. Sep 20, 2022
    Rich M.

    Rich M. Shoe salesman 2022 Sponsor

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  5. Sep 20, 2022
    Jw60

    Jw60 Airbender and interrupter of the light guard. 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I think you need to borrow a mill to drill the bellhousing and a lathe to make an extended pilot bushing...
     
  6. Sep 21, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Bozeman, MT
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    Hey Nick - do you think the AA 23t short input shaft I linked above would work with a v6 and bop bell? Thanks
     
  7. Sep 21, 2022
    colojeepguy

    colojeepguy Colorado Springs

    At the foot of...
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    I'm questioning in my mind whether this swap is worth the effort. I've never driven one but the close ratio T18 has a 4-1 1st gear and a 2.4-1 second. This seems less than ideal to me. You'll only be gaining 0.9 low gear ratio compared to the T14, and that second gear is pretty high to use as a first gear for driving on the street, as you normally would with a granny 4 speed. In my mind I'm thinking it's a lot of work and expense for not a lot of gain.
    On the + side, you'll have a MUCH stronger trans!
    Just food for thought....
     
  8. Sep 21, 2022
    oldtime

    oldtime oldtime

    St. Charles,...
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    IMHO I certainly think it’s worth it under certain conditions.
    No the NR version of T18 is not a rock crawlers transmission.
    The WR T18 has much better gear steps for most.
    The NR T18 has better gear ratios when towing or traveling through mountainous areas where you hope to keep your rpm up into the useful powerband.
    Especially true if you have a D20 which cannot accept a gear splitter and you need one.
     
  9. Sep 21, 2022
    Norcal69

    Norcal69 Out of the box thinker 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    With the increase of .9 in compound 1st gear he's going from a crawl ratio of 47 to 61!
    He's in the 60's....... official wheeling crawl ratio territory.
    In second gear his roll off ratio will be 11.7:1 That's a better roll off ratio than a T14 in first gear with 3.73 rear gears.
    This is the makings for a perfect "all around" jeep!
     
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  10. Sep 21, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Bozeman, MT
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    I kind of don't want to derail this thread too much, but, As Kyle mentioned - we had a thread discussing 'roll-off or start off ratios' awhile ago - and basically, the other than missing the 6:1 granny, the 4:1 gearing is really good from my POV. I've driven my jeep as is with T14, OD, 4.88s and 33s for 8 years and 30k miles, and on pavement, I generally prefer to start from a stop in 1st gear (3.1) plus the OD (which is a 75% reduction - I think). So 3.1 x 0.75 = 2.33.....the 4:1 T18 is 2.41 '1st' gear. I actually think that is a big selling point of the 4:1 T18 - the starting gear isn't so low that I would need to use the OD and I can still get rolling up to a decent speed before shifting into second. Additionally, the 4:1 T18 has a higher 2nd gear of 1.4 vs the 1.6 of the T14 (and the WR T18), which also helps allow for usage without engaging the OD - I would rather not have to always be in the OD until actually needed for going beyond 3rd gear. The disadvantage of the 4:1 first vs the 6:1 first is a definite trade-off, but as I already have 4.88s and 3.15 in the D18, I don't HAVE to have the deeper gearing option, and will still get the CR to over 60:1. Sure, I'd love 90:1 but given I drive it out of 1st gear all the time, and really only need 90:1 crawl in maybe a few spots ever, I can live with the trade-off. I am not saying this is the swap for everyone - if the rig is build solely for 4wd, then maxing out the CR and sacrificing some street drivability makes sense. Or if a jeep has no low gears in the D18 and 3.73, its already got good street gearing and needs focus on the crawl, but in my case, where I drive it tens of thousands of miles on road with 4.88s and have some additional crawl with the D18 low gears, I can find a good balance improving both the crawl and street-ability with this set-up.

    Of course, trying to get the thread back on track, even if all that makes perfect sense for my application (at least from my POV), it may not be practical or doable if I cannot figure out a shorter input shaft, and the extra length is too much for the rear driveshaft. If I can find short shaft or use that AA shaft above, then this set-up has a lot of really good things going for it. I like the 4:1 T18 gearing, its in perfect shape, much stronger than the existing T14, and with a short shaft and direct mounted to the BOP bell, plus the thin OEM D18 adapter, the OAL and reduction to the driveshaft length is quite minimal - like only an 1" or so. Even if I have to spend $250 on an input shaft, the overall cost isn't that bad as I don't need a mainshaft swap or D18 adapter....all the additional hassle and cost of clutch, cross-member and driveshaft is still there. If I can't find a shorter input shaft solution, then how much of an issue is shortening the rear driveshaft by nearly 4"....which seems like a lot, maybe too much.
     
    Last edited: Sep 21, 2022
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  11. Sep 21, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

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  12. Sep 21, 2022
    oldtime

    oldtime oldtime

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    You never mention what engine or bellhousing you want to mate the transmission to.
    GM, AMC or whatever.
    You need to know the exact required stickout length for your engine , bellhouse and if any adapters plates are used.
    Measure from inside of pilot bushing to mounting face if bellhousing. That is your required stick out length. In some instances an extended (protruding) crankshaft pilot bushing may be used if the maindrive gear stickout length is a tad short.
    IMHO the only advantage to 4.02 Ford T19 is the synchro first gear.
    If you always start out in first gear like when having a higher final drive ratio such as 3.73 the Ford T19 can begin to shine otherwise stay with the 4.02 T18.
    4.02 x 3.73 gives you a nice low street driving take off ratio of 14.96/1.
     
    Last edited: Sep 21, 2022
  13. Sep 21, 2022
    Rich M.

    Rich M. Shoe salesman 2022 Sponsor

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    I'm pretty sure all the Ford versions are 6.5" stickout. This is why AA uses an extended pilot bushing with their trans/ bellhousing adapter. Me I would skip the adapter and drill the bellhousing. Use a standard pilot bushing.
     
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  14. Sep 21, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

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    agreed....that is my plan....although the T18 I have has the asymetrical 'jeep' T18 mount pattern, not the ford butterfly, but I am pretty sure it can still be fitted directly to the BOP bell with a bit of work (probably copy something similar to what Roy did - at least I think Roy had that mount pattern).
     
  15. Sep 21, 2022
    Twin2

    Twin2 not him 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    I used a BOP bell to do my initial install with the jeep T18 . one it allow me to look up through hole in bottom to see how thing were going together
    but the frame mounted master cylinder brake line didn't play well with the other start bump
    as to bell housing . had the inside welded up for the jeep bolt pattern . with the one hole behind clutch fork . using a button head allen bolt
     
  16. Sep 21, 2022
    Norcal69

    Norcal69 Out of the box thinker 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    What's the rest of the input shaft diameter? If the blank diameter is consistent with the spline diameter....
    I would consider finding a local machinist to cut the splines deeper, chop with shaft and turn a pilot diameter on the end.
    Bozeman should have a couple old school machine shops.
     
  17. Sep 21, 2022
    Rich M.

    Rich M. Shoe salesman 2022 Sponsor

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    Word. Machining may run you more than an input though. I tried to have a long Jeep t18 cut down once, shop gave up on it. Couldn't get through the heat treating. He said sometimes they can punch through and do it, others were so hard and deep kept breaking tooling. Crapshoot.
     
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  18. Sep 21, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

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    FWIW - the input shaft diameter is 1-1/8" 10spline with 3/4" pilot tip. The 'blank' section of the input shaft has the same 1-1/8" diameter as the spline section....so yes, extending the splines a bit back toward the transmission and cutting the snout 3" or so shorter and machining a new pilot tip could work in theory.
    [​IMG]

    Something else to note...even if I can get input shaft figured out, the jeep T18 asymmetrical mount pattern is problematic - it lacks the middle tab on the passenger side that Roy shows here, so direct mount to the BOP bell is going to be a bit more difficult. No option for this trick:

    [​IMG]

    And also no lower hole or tab on the driver side.....Novak makes some bridges kind of like what Roy did...
    [​IMG]

    And I've seen Ken's solution - but that is out of my league:
    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]

    I think I am back to I'd rather just drive my jeep as is...
     
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  19. Sep 21, 2022
    Warloch

    Warloch Did you say Flattie??? Staff Member

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    James - if your going to be back down this way, I have a T19 out in the shed with "I think" the 4.02 first gear. I would need to count the gear teeth as it's been years.

    Yours if you want to drag it home as I've no plans for it now.
     
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  20. Sep 21, 2022
    Norcal69

    Norcal69 Out of the box thinker 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Herm welds an ear onto his T18 cases that utilizes the BOP mounting hole.
     
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