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Thread: LSD for the D27

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    Default LSD for the D27



    Just beginning to think about a powerlock (limited slip) install for the D27 in the front of the cj5...pick up a used unit that I am working on disassembly and cleaning. It was already partially disassembled when I got it, so not 100% sure exactly how it all goes back together! I think I found all the pieces....a few of the clutch disks are grooved, but some new clutches and I think it should all work fine....My plan is to get the new disks and bolt the case together on the bench when I have time this winter, then when I a have a bit more time, I'll have to pull the front axle out of the cj, and swap the case in place of the OEM open case, moving the ring gear over to this unit.....that of course essentially means a pretty big job with new carrier and pinon bearings, and going through resetting shims for backlash. Having done it previously for the e-locker install in the rear, its a lot of work, but hopefully not as intimidating the second time around....we'll see....dropping a lock-rite auto pin into the existing open carrier would be a lot easier, but not nearly as classic, and this case is much stronger than the open unit and helps reduce shock load on both the case and the axle shafts (which are also a bit weak).



    FWIW - the cross-shaft with the 4 small pinon gears has a hole through the center with a spacer pin (thrust block) in it suggesting this unit was originally used in a rear tapered axle....D27s were not a common rear axle, so guessing this unit might have original been in an early Scout 80 - one of the few D27 rear axle vehicles. For my use, the thrust block will just get pulled and the hole left open (I believe that is because the front axle is full float and the rear axle would have been semi-float).

    Allright, back to cleaning parts and seeing if I can figure out loose re-assembly while I find some new clutch disks.
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    James Orofino
    1970 CJ5
    1958 Willys Wagon

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    Default Re: LSD for the D27



    if you are into vintage information pamphlets etc....here is one for the Dana Powerlok
    These were mostly used in D44 and bigger rear axles (and some version of them still exists today), but mostly IH and military jeeps had them in D25/27/30 front ends as well. If this goes well, I have a unit for a D44 that will go into the 58.
       
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    James Orofino
    1970 CJ5
    1958 Willys Wagon

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    Default Re: LSD for the D27



    Had a little time to mess with this....I decided to spend a bit of time figuring out how everything fits together and what is the best way to assemble it - especially considering once you are doing it for real, it will be a bit oily, and as it takes both hands, getting photos would be difficult. The basic idea is straight forward - its the actually number of hands and fingers and position of everything that makes it a bit of a finnicky PITA. ALthough I did the eaton e-locker install on the D44, that was just a case swap - I've never pulled the internal of the case apart and messed with the side and pinon/spyder gears. For those interested in my dry test fitting:
    The is sort of the key piece - its the side gear ring/hub (#7 in the FSM diagram):


    as you can see it has both external splines and internal splines. The external splined hub is where all the powerlock clutch pieces ride....the 3 plates (with tabs) are not splined and just slide over the splined ring hub. The 2 clutch plates in between the plates are splined and mesh onto the ring splines.


    On the flip side of the side gear ring is where the actual side gear sits:


    the internal splines of the side gear and ring must mesh with the axle shaft that goes through the middle - thus the need for some sort of axle shaft during assembly. When things are tightened down, if these splines are not aligned, the axle shafts will not slide into place inside the case.


    NickM is lending my some set-up stubby axle shafts so I can do this on the bench and not have to pull the shafts out of my cj....the set-up sort of begins to look like this:


    Of course, the reality is that when you try to slide things into place, everything sort of falls apart (mostly the clutch disks and plates slide off the side gear ring).....so here is what I found seems to work best.....First, drop the outermost thin clutch plate down into the case halve:


    Then slide the remaining clutch pack and side gear ring into place - seems to work best doing this sideways so the splined clutch pack pieces don't fall off:


    The key part here is to make sure the clutch pieces stay in place and getting the entire pack to sit all the way down to the bottom of the case....


    Then you can slide the axle shaft up through the case - but don't push it too far through to the end of the splines such that it pushes the clutch pack out and the pieces fall off the side gear ring hub!.....when its all done with side gear and spyder gears in place:


    As this is for a full-float front axle application...leaving the pin out of the cross-shafts.....And of course, the part that I can't get a picture of as I need too many hands, the other half of the case will mate to this half and bolt together......that D27 lock-rite is looking easier and easier....

    So my question for tonight....I hope to finalize the assembly on my next day off. I understand I will need to soak or at least coat the clutch disk pieces in appropriate gear oil (with LSD additive)....Do people actually let this soak overnight, or just use some liberal coating during assembly. Along those lines, my intention is to finalize the assembly and then set the case aside on the shelf for a few months until I am ready to pull the front axle out of the cj and do the case swap etc....any issue with that? I figure most of the oil will drip off and out, but at least a little will hang in there for a few months?
    ___________
    James Orofino
    1970 CJ5
    1958 Willys Wagon

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    Default Re: LSD for the D27



    Wonderful photos and description!

    I can't offer any answer to your questions though, sorry.

  5. The Following Member Says Thanks to Jim For This Post:

    FINOCJ (January 4th, 2023)

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    Default Re: LSD for the D27



    Very interesting! The only comment I can add is that the transfer case I bought for my swap sat (drained) for over 10 years at the used parts store. I added some fluid and rotated the input shaft by hand a little before bolting it in, and it works just fine, granted its only been a few hundred miles so far. Cars sit all the time for months or years and you usually don't have an issue with the differentials, would this be any different?

  7. The Following Member Says Thanks to Mountaineer01 For This Post:

    FINOCJ (January 4th, 2023)

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    Default Re: LSD for the D27



    Mountaineer01 previously posted:
    "Cars sit all the time for months or years and you usually don't have an issue with the differentials, would this be any different?"

    Only that its not sitting inside the differential carrier in the fluid....the case would be stored on a shelf and most of the fluid will drain out of the case, and of course, dirt and dust can get into the case easily enough as well....As I understand, the biggest issue is that the metal clutch disks need the appropriate lubrication between them from the start. A 'dry' start can cause pretty significant damage immediately (kind of like a dry start to a fresh engine - thus oil pump priming is done). So basically, upon assembly, each disk needs a coating of the proper LSD gear oil (fiber disks are supposed to soak overnight for full impregnation). Typically, you'd install the case into the carrier and start driving it reasonably soon...after that, even if the car is not driven a bit, the initial break-in of the clutch disk surfaces have occurred (like ring/cylinder break in) and then things are pretty good....the case is of course then sitting in the differential carrier where its half or slightly more submerged in gear oil, and one could spin the axle by hand to get some fluid movement. Anyway, its not too big of a deal - going to assemble per FSM instructions with LSD gear oil on the metal disks, then will put in a ziploc inside a sealed plastic bag to keep the dirt and dust out while it sits on the shelf for a few months. If I am really concerned about it, I could most likely use just a bit of petroleum jelly between the disks....this is SOP for assembly of old school transmission and transfer cases with yellow metal parts. It dissolves (not really right word - maybe emmulsifies?) easily into the gear oil (unlike typical moly grease) and provides good protection during the first few seconds of initial start up before gear oil can be slung everywhere, but it doesn't have the proper LSD friction additive.
    ___________
    James Orofino
    1970 CJ5
    1958 Willys Wagon

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    Default Re: LSD for the D27



    Time to panic a bit.....or at least swear a bunch and walk away until my next day off in 2 weeks....
    Have an issue....I broke a small tab on the ring gear side of the case when tightening the two case halves together....how much did I eff it up? Did I just waste the case?


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    1970 CJ5
    1958 Willys Wagon

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    Default Re: LSD for the D27



    This has been sitting on my mind since you posted it. My stance now - it's of very little consequence / I wouldn't worry.

    Why? It seems it's more of a "locating upon assembly" lip of metal than anything needed for use. I see a substantial bolt hole right next to that lip - and similar bolt holes around the ring. Those bolts, when tightened, will be locating and holding the two parts together - that thin lip of metal likely would not be in contact with the metal of the other half (perhaps a few thousands of an inch between). The remaining lip of metal would be sufficient to tend any locating task.

    As for "out of balance" issues - nope. Yes, it's a rotating mass, but the overall mass is significant in relation to the trivially small missing lip.

    Am I missing something here?


    secondly - what's up with the heat marks near that lip (both halves)?

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    Default Re: LSD for the D27



    Calling it good...I went down the wrong road on this thing a couple times, and also managed to mangle some of the original hardware and do some damage to the case itself. But I think its going to work. The hex heads are smaller than standard to allow for the ring gear to slide over the case.....

    so I replaced all the hardward and used the standard size head on the hex bolts as it was all I could get easily - so may need to grind a corner off a couple of those if the ring gear won't clear.....red loctite is setting up.

    Then I should be able to pull the stub shafts and send them back to the loaner. The case can be set aside for a bit now until I am ready to pull the current case etc - I am assuming the internals won't loose their alignment sitting on the shelf.
    ___________
    James Orofino
    1970 CJ5
    1958 Willys Wagon

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    Default Re: LSD for the D27



    Any machinist in town - one that could shave the faces on the large hex to match the small hex?

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