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Let's Talk T18 and T98

Discussion in 'Early CJ-5 and CJ-6 Tech' started by DanStew, Sep 7, 2007.

  1. Sep 7, 2007
    DanStew

    DanStew Incorrigible. Staff Member Sponsor

    Lexington, South...
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    i was looking at pics and thinknig bout this. so the way it sits now. with the small bearing in my Tcase and the large gap. I am guessing the nose part of the main shaft is not sitting fully inside the input shaft, it is only riding on 3/4 of the bearing face of the 22 needle bearings in the input shaft. So with the larger bearing it will push the input shaft farther back to fully seat the nose of the main shaft? Is this correct thinking? I am just trying to picture how the larger bearing makes a differnce.
     
  2. Sep 8, 2007
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
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    You got it! It took a bit of rereading the posts for it to dawn on me.
     
    Last edited: Sep 8, 2007
  3. Sep 8, 2007
    nickmil

    nickmil In mothballs. Sponsor

    Happy Valley, OR
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    Clint,
    The top transmission is simply a late model T-18 case and top which has reverse over and down as you noted. The earlier T-18's didn't have that big bulge in the side where the reverse fork goes down the side of the case from the top and the Jeep T-98 and T-18 cases were visually almost identical and reverse was over and towards the dash. They have the smaller bulge towards the bottom of the case for the reverse idler gear. The earlier T-18's frequently came from the factory with T-98 tops. They are that similar. Its just the guts that are different.

    Dan, the thinner front bearing is a 6308.
    I just looked up the rear bearing #and it's listed as a 308-L according to the book. The thicker front bearing is the same bearing as the rear output. Nickmil
     
  4. Sep 8, 2007
    xlr8n

    xlr8n Member

    Sparks, Nv.
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    148

    Correction to the bur location from the quote above. The bur was on the input shaft where the seal rides and not the case (my memory of this episode is coming back clearly now).

    BTW - I think have a wide front bearing laying around if you want it. Albeit it is used it is still in good shape. Simply pay shipping from 89441 and it's yours.
     
  5. Sep 8, 2007
    DanStew

    DanStew Incorrigible. Staff Member Sponsor

    Lexington, South...
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    Thanks! But i am going to get a new one just for cheap insurance :) But thank you for the offer.
     
  6. Sep 22, 2007
    DanStew

    DanStew Incorrigible. Staff Member Sponsor

    Lexington, South...
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    Hey Nick, is that a timken nubmer or federal mogul? We have an in town bearing house that can probably get me the bearing but just curious for what books they should look for the nubmer in.

    I finaly got the Tranny out of the jeep. I really need to put a filter on my breather, that oragne stuf turned out to be dist from the trails i have been going in lately. The Tcase is nice and clean :)

    But boy does gravity help to get a tranny out of the jeep.... i just dread installing the thing again :(

    Oh well... i am just a bit closer to getting it done :)
     
  7. Feb 18, 2019
    Mike Dreuth

    Mike Dreuth New Member

    Rhinelander, WI
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    I know this is an old thread, but I am also having input bearing problems with my T98. Bought the AA 712512-T98 and rebuilt kit from Herm. Rebuild went good considering I've never done this before. When I installed the input bearing (thin) the oil slinger is very loose, and it doesn't seem like the input shaft is fully seated in the main shaft. Nowhere in any instructions from AA, or any where else beside this thread can I find info on this. Do you think it's possible I need a thick input bearing, as I believe the new input shaft is from a T18. The confusing part is they appear identical except the original T98 is loger and different spline count. The other difference is you have to change the rollers inside the input.
     
  8. Feb 18, 2019
    oldtime

    oldtime oldtime

    St. Charles,...
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    Internal and external T98 / T18 Ford, Jeep, IH and other make parts may or may not interchange.
    Lots of similaries and differences over the years and by the various makes of Borg Warner T98/T18.

    I'm not familiar with the AA kit you have .
    But that kit was apparently intended for T18 transmissions not T98.
    So I'm guessing that your main drive gear pilot bearings could certainly be a real issue.
    The maindrive to mainshaft pilot bores and roller bearings were often of different sizes depending on specific make and model.

    You say you have a T98 case but what internals ?
    Jeep, Ford, IH, or other some other make or some other mixture of components.

    The proper bearings for a Jeep T98/T18 are:

    GROUP 17-02
    912362---------------T98 maindrive---------------------------------------------MRC 308 SG 2
    912362---------------T15/T18 maindrive---------------------------------------MRC 308 MG 4

    GROUP 17-03
    912341---------------T98 mainshaft---------------------------------------------MRC 308 SG
    912341---------------T18 mainshaft---------------------------------------------MRC 308 MG

    BALL BEARING INTERCHANGE CHART

    FAFNIR.......MRC.........SKF............TIMKEN..........FM...........BCA
    308KG........308SG........6308NRJ.........308L..............308LI........308L3
    308KG2......308SG2......6308NRJX.......308LI.............308LI........308LIN3
     
  9. Feb 18, 2019
    Mike Dreuth

    Mike Dreuth New Member

    Rhinelander, WI
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    This a true virgin T98 case and internals taken from a 65 CJ5 .I have all original parts, floorpans, driveshafts, crossmember, shifters. I just spoke to AA and they stated I need a "308" bearing without oil slinger. Not sure what that meant, or why it wasn't in the instructions as this was a specific 712512 T98 kit. I assume a thicker bearing. I questioned the slight "play" in the needle bearings between input and mainshaft. I was told this is normal.
     
  10. Feb 18, 2019
    Mike Dreuth

    Mike Dreuth New Member

    Rhinelander, WI
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    Thanks for the info oldtime. I really like the information in this site, and no flaming like other sites. AA called Herm about this issue after I called them. I would say Herm (Adam) are true experts if AA calls them. Steve is a good guy from AA though. Herm is swapping out the input bearing for the price of shipping. Can't wait for this to be done.
     
  11. Feb 18, 2019
    oldtime

    oldtime oldtime

    St. Charles,...
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    I've got both T98a and some T18's also.
    Hard to locate these but I like to run OEM NOS Fafnirs #1
    Will also use MRC #2 choice when I can find them.
    Other brands may be as good but are not OEM parts.
     
  12. Feb 20, 2019
    MarkMac

    MarkMac New Member

    Okotoks, Alberta
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    I am not sure if this is on topic or not. I am a recent owner of a '56 CJ5. I want to change the transmission to a Ford T18 (1970 build date). I have a friend with a Jeep T18 and Dana 20 transfer case, that I can pick up for next to nothing. It has the close ratio trans. Now my question. Does my friends Jeep T18/Dana 20 have the necessary adapter and shaft for me to mate the Ford T18 to my Dana 18? Talking T18's and all.
     
  13. Feb 20, 2019
    oldtime

    oldtime oldtime

    St. Charles,...
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    Yes the Jeep mainshaft and Jeep rear adapter plate regardless of the year of manufacture should mate to any Ford T18.
    Obviously the Ford T18 case casting must be drilled and tapped to accept the Jeep rear adapter plate.
    Or you can put the Ford internals into the Jeep T18 case if you prefer doing it that way.

    Your engine bellhousing may influence your case selection.
     
    Bowbender likes this.
  14. Feb 21, 2019
    MarkMac

    MarkMac New Member

    Okotoks, Alberta
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    Thank you oldtime for the info. I was confident that would be the case, but have invested many an internet search night trying to find the answer. Sometimes, in the right company, it pays to ask.
    MM
     

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