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D30 yoke question

Discussion in 'Early CJ5 and CJ6 Tech' started by termin8ed, Dec 14, 2005.

  1. Dec 14, 2005
    termin8ed

    termin8ed I didn't do it Staff Member

    Mason, MI
    Joined:
    Dec 22, 2002
    Messages:
    4,422
    OK, I've studied up on this a little now, but just a couple questions for everyone. I've measured the yoke on my d30 and it seems to be the same as the yoke on my 68's d27. All I can see is that it might be the yoke that uses the straps instead of the u-bolts.

    I've read where you need to swap out the yoke on the d18 with the d20 yoke and use a different driveshaft. Is there a reason to this as far as the D30 being a longer diff case? Or is this for a newer d30?
    I've got one of the first years set up with drum brakes originally(and still is...)

    I know about the spring plates also.

    I'm assuming by looking at the parts catalogues that the gears are not interchangeable between the d27 and d30?
    Preciate the help. Probably won't be till spring once I get it installed, but Trying to get parts and stuff now for the swap.
     
    termin8ed, Dec 14, 2005
    #1
  2. Dec 14, 2005
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
    Joined:
    Jul 30, 2003
    Messages:
    8,524
    all CJ yokes used the ubolts I believe, 1941-1986.
    with the exception of the small V6 front d/shaft u-joints, all the u-joints were the same, 1941-1986
    so the yokes bewteen the D18 and D20 would use the same ujoint.
    the only difference I can think of would be the spline count between the 2 yokes, maybe length/depth also, but that should be minor.
    gears between D27 and D30 are different
    sorry, haven't been reading up on what you are trying to do
     
    jpflat2a, Dec 14, 2005
    #2
  3. Dec 14, 2005
    lynn

    lynn Time machine / Early CJ5 HR Rep Staff Member

    Huntingdon PA
    Joined:
    Sep 20, 2002
    Messages:
    3,437
    If your '68's D27 came from a 4-cyl., then it ran the larger ujoint. And the yoke on the Tcase will accept the same size joint as the one used on the D30, so the original driveshaft will be OK.

    As Jim said, the V6 units used a skinny driveshaft/smaller ujoints... so when you go to swap a D30 in, your V6 DS and joints will not work. Also, the front output yoke on the V6 D18 needs to be changed from the smaller V6 ujoint to the larger one as used on all 4 bangers and all later D30s.
    IIRC this is the only reason to change yokes/DS when doing a D30 swap. I don't recall the pinion end being that much longer that the 4 cyl DS can't be used once the D18 small yoke is replaced.

    Straps instead of ubolts.started showing up on yokes about 1980 or '81
     
    lynn, Dec 14, 2005
    #3
  4. Dec 14, 2005
    Bob

    Bob Member

    Northern California
    Joined:
    Sep 23, 2002
    Messages:
    439
    My D30 is out of an '81 and it had the yoke for straps. I swapped it for a u-bolt yoke from a friend's '72 Scout D30. I guess I got lucky or my '66 V6 is some kinda freak because my D18 already had the large u-joint yoke. It's an original V6 Jeep and was built in either November or December of '65. Maybe some early V6's still had the large 4-cyl. u-joints.
     
    Bob, Dec 14, 2005
    #4
  5. Dec 14, 2005
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
    Joined:
    Jul 30, 2003
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    8,524
    just to confirm what Lynn has said, the straps did start in 1980 per the book
     
    jpflat2a, Dec 14, 2005
    #5
  6. Dec 15, 2005
    termin8ed

    termin8ed I didn't do it Staff Member

    Mason, MI
    Joined:
    Dec 22, 2002
    Messages:
    4,422
    Might've been wrong about the straps. Probably was...

    Guess I'm lucky too. I measured the yokes for the u-joint and they are the larger ones. 3 1/2" across, about 1 1/8" diamiter(roughly). I did measure the 69 I have with the hurricane and it has smaller ujoints. Maybe thats more of a year thing than 4/6cyl?
    At any rate, sounds like I don't have to worry about that now:)
    Just need to re-gear and get the ubolts for the axle.

    Thanks for the clarifications guys8)

    Mostly collecting parts up till now. Planning on swapping the back axle out and put one that has 4.27 gears, I've got a D27 I'm going to put up front right now untill I can buy a new gear set for the D30. Maybe a locker of somesort too. Then the OD will go on also8)
     
    termin8ed, Dec 15, 2005
    #6
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