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Power To The Front Wheels But Not The Rear

Discussion in 'Early CJ5 and CJ6 Tech' started by WPcj5, Nov 6, 2021.

  1. Nov 6, 2021
    WPcj5

    WPcj5 New Member

    Tennessee
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    Apr 5, 2021
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    8
    I finally got around to testing the drivetrain on my '70 cj5 and for some reason only the t-case driveshaft/yoke spins. No power at all to the back wheels, in any gear. Could this be a clutch issue? it's a T-90(a1) transmission. Appreciate any input.
     
  2. Nov 6, 2021
    boopiejones

    boopiejones I can’t drive 55

    California east bay
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    Mar 16, 2020
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    When you say “only the t-case driveshaft/yoke spins,” are you referring to the front or rear t case output?
     
  3. Nov 6, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Denver, CO
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    Might have to give us a bit more information on the entire set-up...If its a t90 transmission, then is it a 4cyl? Originally, a 1970 would have had a D18 transfer case, and thus both the front and rear driveshaft is driven from the transfer case, and both outputs would be offset to the passenger side. I mostly ask as its possible that parts have been swapped out etc, and it will be more helpful if we know what transfer case we are dealing with.
    this is the part that we could use a bit more explanation....do you mean is it only the front t-case yoke/out put that is spinning? If the front is spinning (in 4wd) but the rear is not, then I don't see this as a transmission or clutch issue - but rather something internal to the transfer case, but I suspect there is something else going on elsewhere and we need a bit more info on the entire set-up.
     
  4. Nov 6, 2021
    Oldpappy

    Oldpappy A.C. Fults - Curmudgeon at large 2021 Sponsor

    East Tennessee
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    Not a clutch issue or the front output yoke wouldn't spin, but as said we need to know which Transfer Case you have.

    Which part of Tennessee are you located in case you need help?
     
  5. Nov 6, 2021
    WPcj5

    WPcj5 New Member

    Tennessee
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    Apr 5, 2021
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    8
    Sorry about that, the setup is:
    f134 4cyl
    t-90a1 trans
    d18 t-case (single stick if that matters)

    Right now only the yoke to the front wheels turns. The yoke to the rear wheels doesn't. The t-case has one of those drum brakes for the parking/emergency brake on the output shaft which is connected to the rear yoke and I haven't messed with it yet but that drum and the rear shaft doesn't seem to budge even a little when the engines on.

    For further explanation, I can turn on the jeep and engage 4 high and the front yoke spins. But this can be while the trans is in neutral. The trans shifter doesn't seem to do much of anything. Neither does the clutch. Now I'm out of town and I won't be home until Wednesday but I'll try to keep explaining as much as I can from memory for now so hit me with any other questions you have. I'll try to answer with what I found out from the limited testing I've done.
     
  6. Nov 6, 2021
    WPcj5

    WPcj5 New Member

    Tennessee
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    Apr 5, 2021
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    See my other reply for the setup and more explanation. As for help, I have buddies who can help me and I should be alright once I actually figure out what's going on, but thank you anyway.
     
  7. Nov 6, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Denver, CO
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    hmmm....if the transmission is in neutral, you shouldn't have either front or rear outputs spinning... How are you 'testing' this? I assume you have the driveshafts disconnected at the transfer case yokes, and with the engine running/idling, you are working the clutch and shifters? When you say an output spins, do you mean its free to spin by hand, or it spins under power from the engine?
    I am beginning to wonder if with the single stick, when you think you are shifting to 4hi, you are really shifting into neutral and the parking brake is limiting the rear output? The single stick has 4 positions - the forward most is 2hi, then 4hi, then neutral, then 4lo as you pull it back away from the firewall....the 2hi position is way far forward towards the firewall, farther than some people think.

    As a side question - maybe more for forum members - I was thinking the F134 never came with a single stick D18? That only the large case D18 (standard with v6) came with the single stick, whereas the F134 always came with t90 and small case D18 with twin stick....the reason I am wondering is if someone swapped around the shifters in some way, if they didn't get the shift rails in the right position with the detent balls or something like that, or one of the shift forks is messed up etc? I've only rebuilt a couple D18, but I am struggling to remember if its even possible to get the front output to engage without the rear output? But there is still the issue with the transmission being in neutral...
     
  8. Nov 6, 2021
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Hills of NH
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    How are you "testing" this?

    By "spin" is it really solidly powered up, or is it maybe just getting a little rotation from the oil dragging, while the rear shaft is restricted by the e-brake?
     
    Geo likes this.
  9. Nov 6, 2021
    WPcj5

    WPcj5 New Member

    Tennessee
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    Apr 5, 2021
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    To clarify, "Spinning" means that there is absolutely power going from the engine to the front yoke. I was testing it with the front driveshaft off because of bad/loose U-joints and the rear shaft connected. I could drive the car in 4wd if I wanted to, I'd only have to reattach the front driveshaft, but only the front wheels would turn.

    Again, this is just off of what I remember during the couple hours of testing that I managed to do before I left. As far as I can remember, the front yoke spins under engine power even if the transmission is in neutral, when 4wd was engaged.

    lots to address here. I'm pretty sure I was correct on the shifter positions as I was doing the tests, but I could've been wrong. I know for a fact that I shifted up (towards the firewall) and the front yoke started spinning though.

    As for the transfer case not being original, that could be very possible. I got the jeep from someone who bought it as a project from someone else who also had it as a project. It had no wiring, fuel tank, etc when I got it and it was lifted 3". There was even a tiny turbo under the hood (now disconnected) which was hooked up to an aftermarket exhaust setup. So there's a good chance that the transfer case isn't original or was messed with and/or installed wrong.
     
  10. Nov 6, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Denver, CO
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    Just to ask - have you confirmed it is a D18 transfer case? I know your not with the jeep currently, but some pics would probably help avoid any obvious mistaken identification or something like that.
     
  11. Nov 7, 2021
    WPcj5

    WPcj5 New Member

    Tennessee
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    I managed to find some pics on my phone from April, back before I replaced the rear driveshaft ujoints and the missing t-case shifter. 20211107_100137.jpg 20211107_100115.jpg
     
    FinoCJ likes this.
  12. Nov 7, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Denver, CO
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    Thanks - as you reported, its a D18 with single stick front cap. I am still not sure if that single stick front cap would have been original on a T90/D18 combo...Also have you tried putting the transfer case in neutral and turning the outputs by hand? Be good to know if the rear output will turn at all, or if the brake has it frozen up or if its bound up internally. Kind of figuring at this point, when you get back to the jeep, you can put the transmission in neutral (engine off), and then shift the transfer case through its 4 positions turning the front and rear outputs by hands, and watching the shift rails as well.
     
  13. Nov 7, 2021
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    Is it possible to disconnect the rear axle of a Dana 18, and connect the front? I did not find any good diagrams, but it looks like there are two selectors. The one on the input shaft selects high range (beveled gears engaged), neutral (no gear engaged) and low range (straight cut gears engaged). Then there is a collar on the front output shaft that connects the front axle, or not. I don't see how this provides front only. If the intermediate gear is powered, the rear axle is powered.
     
    Last edited: Nov 7, 2021
  14. Nov 7, 2021
    timsresort

    timsresort Member 2021 Sponsor

    South Lake Tahoe CA
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    Well, that is an 18. The front output and rear output are connected when in 4WD, so both have to drive, if truly in 4WD. I agree with the neutral idea, it may just be spinning with oil. Try to spin it by hand, or hold it from spinning.
     
  15. Nov 7, 2021
    jeepdaddy2000

    jeepdaddy2000 Member

    Eagle Point oregon
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    Lets troubleshoot.

    Put the trans in gear and the t case in 2 high:
    Does the front yoke rotate?
    Does the rear yoke rotate?
    The front should rotate
    The rear should not rotate.
    If the rear does, then drop the t case rear cover and observe the bull gear while rotating.
    If the bull gear rotates, then the issue is in the transmission.
    If it doesn't, the issue is in the t case/linkage

    Do the same process with it in 4 high
    Does the front rotate?
    Does the rear rotate?
    If one does and the other doesn't, then the issue is in the t case.

    Drop the bottom cover and rotate the rear yoke.
    Is a drive/driven gear stripped?
    Is a sliding gear not engaged?
    If a gear isn't engaged, move the the shifter and observe the yokes.
    Are they moving?
    Is the rail moving but not the yokes?
     
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  16. Nov 7, 2021
    SFaulken

    SFaulken Member 2021 Sponsor 2020 Sponsor

    Marysville, WA
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    I don't *think* that's possible, at least not with the parts provided in a stock configuration. You'd have to do some serious re-engineering on that output shaft setup to be able to drive the front driveline, without driving the rear. You'd almost have to duplicate the front disconnect setup on the rear output.

    Yeah, actually, thinking about it some more. It's basically impossible on a D18, to have the front output being driven, and not the rear, unless the output shaft is just broken. If the transfer case is turning, no matter what you do with the the Front Axle Disconnect or Range Selector, the rear output is going to be turning, if it isn't.
     
    Last edited: Nov 7, 2021
  17. Nov 7, 2021
    Jw60

    Jw60 WRPD855 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Sedalia MO.
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    A 4cyl tux would be single stick d18.

    I seem to think it was a column shift trans 60/40 bench thing.

    I'ld order up a gasket kit to be there when you get home. It's gotta come apart to really know what is happening.
     
  18. Nov 7, 2021
    duffer

    duffer Rodent Power

    Bozeman, MT
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    Yep. Even if you left out the sliding gear that wouldn't work as there would be no way to engage the front output shaft. Back to the question are we certain it's a D18?
     
  19. Nov 7, 2021
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    If I remember correctly my new '69 4 cyl. had a single stick case. The older ones were of course dual stick.
     
  20. Nov 7, 2021
    jeepdaddy2000

    jeepdaddy2000 Member

    Eagle Point oregon
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    See post #11
     
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