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T-18 in place of SR-4

Discussion in 'Intermediate CJ-5/6/7/8' started by CJ-X, Jun 7, 2011.

  1. Jun 7, 2011
    CJ-X

    CJ-X Member

    Ohio
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    Aug 6, 2006
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    817
    I have someone interested in purchasing a T-18 from me and installing it into a 1981 CJ-7 that currently has an SR-4 transmission. We need to know what needs to be done to fit it in.
    The T-18 is still installed in the jeep right now. Here are it's details without me taking any measurements.

    The T-18 case itself originated in a 1975 CJ-5.
    The gears installed are from a 2wd Ford pickup (6.32)
    The length of the input shaft is such that it reaches through a standard Chevy bellhousing perfectly.
    The front bearing retainer currently installed fits the chevy bellhousing big hole perfectly.
    I had to make modifications to the bellhousing to bolt them together.

    I hope these "clues " help. Is this as simple as using a T-150 bellhousing?
     
  2. Jun 7, 2011
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    Which engine?
     
  3. Jun 7, 2011
    CJ-X

    CJ-X Member

    Ohio
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    Sorry. He has a 258 cid.
     
  4. Jun 7, 2011
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    Nick should weigh in on this, but I recall that the SR4 bell casting is the same as the T176 casting. So he should be able to redrill the bell he's got to bolt up to the Jeep case. The Jeep case will require an extra hole in the T176 bell anyway. Don't know about the bearing retainer alignment ... I presume it's ok.
     
  5. Jun 7, 2011
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Ok, here we go. The sr4 used a Dana 300 transfer case which will require a transmission output shaft and adapter change. AA and Novak make kits for this. Once this kit is installed the trans length is within 1/4" of the original trans. You can redrill and tap the sr4 bellhousing for a ford t-18. The bosses are cast in for this. My understanding is you can redrill for the Jeep case although I've never done it myself as we use Ford cases for this conversion. From the info you've given your trans is adapted to a 20 transfer case and the Jeep 300 transfer case will not bolt up. If the purchaser is ok with using the Jeep model 20 then the combination is shorter and will/may require driveline mods. He/she also needs to be aware that the 20 has a 2.03-1 low range vs the 300's 2.62-1 low range. Floor mods will be necessary for the Transmission shifter as well. Depending on which way he goes floor mods formthe transfer case shifters may be necessary as well.
     
  6. Jun 7, 2011
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    To add to this, if you used the ford input shaft the length and spline count will work with his sr4 bellhousing but will need a custom pilot bushing available from R&P, Partsmike,'and others
     
  7. Jun 7, 2011
    CJ-X

    CJ-X Member

    Ohio
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    Thanks Nickmil.
    I have a good dana 20 for him with bronco gearing and factory twin sticks. Your comments bring a couple questions to mind.

    1st; What about the size of the big hole in the bellhousing. Will it be the same as a chevy? I think for some reason I could not re-use the original jeep t-18 retainer and I do not know where it is at.

    2nd; I recall, that for some reason I could not use the ford case when I did the conversion. I think it had something to do with how it connected to the Dana 20 but I am not sure. I still have that case. Would it work for him? With either T-case?

    Thanks
     
  8. Jun 8, 2011
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
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    If you used a stock small hole gm bellhousing (car or sm420 style) the ford front bearing retainer would have had to be machined. A stock ford t-18 bearing retainer works fine for the amc bellhousing from t150 up to t5. The ford t-18 case would work great. To use the factory 20 adapter you must drill and tap 6 holes on the back of the case. The factory adapter works good as a jig. Just need to use the output bearing to center everything. You must also plug the bottom left hole in the back of the case or you will have a leak that will drive you nuts trying to find. The gasket doesn't quite seal this area even though it looks like it does. I use a set screw with the threads "distorted" and with sealer to plug this hole. I then fill the set screw with sealer when I install the gasket and transfer case. This takes care of the issue
     
  9. Jun 8, 2011
    CJ-X

    CJ-X Member

    Ohio
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    Pretty sure I used a larger hole chev bell housing.
    Sounds like I may need to find an sr4 bell housing and just see how it fits with the jeep t-18 case.
     
  10. Jun 8, 2011
    Chuck

    Chuck Sponsor

    Southshore Ma
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    You will have to modify the stock skid plate as well. Either mod the center mound on the skid (tranny mounting point will be rearward of the mound) or move the skid plate back and drill new holes for the frame rails.
     

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