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Knuckle studs...again

Discussion in 'Early CJ5 and CJ6 Tech' started by colojeepguy, Dec 31, 2014.

  1. Dec 31, 2014
    colojeepguy

    colojeepguy Colorado Springs 2019 Sponsor

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    I'm getting ready to work on my D27 front end. The front power loc is very loose. so I'm going to replace the clutches. While I have it apart, I'm planning on doing the knuckle stud conversion as well. I know there used to be a write up about doing this on the old earlycj5.com website, but I can't find it anymore...is it still floating around the interweb somewhere?
    Also, what is a good source for D27 powerloc clutches?
     
  2. Dec 31, 2014
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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  3. Dec 31, 2014
    djbutler

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    My preferred method of doing the knuckle stud conversion doesn't involve using press in studs, but rather I use 3/8 X 24 button head cap screws 1 1/4 inch long. The advantage as I see it is that you keep your existing threads, so you don't weaken your knuckle casting, and this dosen't involve using a press.

    I got a counterbore cutter from Machine shop Discount Supply. This link shows the page for the 5/8 counterbore cutter I used. http://www.msdiscount.com/columnar.aspx?cat_id=1108&category_site=STARTOOL
    I also got a 3/8 pilot to fit that counterbore cutter.

    You can use the counterbore cutter in any drill press to face the inside of the knuckle holes just enough to get a square shoulder for the head of the button head cap screws to seat on. You will also need to use a 3/8 drill to cut the top 2 threads from the inside face of the holes so the screws can seat all the way down flush.

    The heads of the screws may be a little larger than 5/8, if so use a grinder wheel to reduce the diameter of the edge of the button head. I used a drill to turn the screws as I pressed them up to the grinding wheel, this also helps to keep your fingers out of the grinding wheel.

    Once the screws are ready, do a trial fit to make sure they seat all the way down flush, then use some locktite for the final install.

    There will be some interference with the heads of the screws at the 3:00 and 9:00 positions against the ball end of the axle. I used a small grinder to clearance these enough to restore the knuckle movement back to original. You can grind on the head of the button head screws or the edge of the ball end of the axle, or some of both. If you grind on the ball end of the axle be careful not to take too much.

    While you are this far into your axle make sure to check and probably replace the king pin bearings and races, and get the preload on these bearings set to the FSB spec.

    Don
     
  4. Dec 31, 2014
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
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    A piece of advice order your button heads from someone like MSC and get american made bolts like camcar, holokrome or such. Do not go to fastenal, they sell nothing but Chinese bolts from my experience.
     
  5. Dec 31, 2014
    colojeepguy

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    Thanks for the link, Tim, that was the section I was looking for but I don't see the specific article I was remembering either. Vernco site showed the press in stud setup....I'm planning on using the button head bolts as djbutler posted above.
    I have a pretty good idea of what's involved but I'd like to have part #s and the exact procedure involved.
     
  6. Dec 31, 2014
    supertrooper

    supertrooper Member

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    Jp magazine has an article with part numbers. Should be able to find it the the tech archives.
     
  7. Dec 31, 2014
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
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    And here is what I have saved - sorry - no pics.

    Dana 25/27 Front Axle Knuckle Bolt Upgrade© 2005 Joe Radwanski
    Edited by Sparky

    Improvements to the early Jeep CJ steering knuckle to spindle connection.
    Acknowledgments
    First, I would like to thank Vern (http://www.vernco.com/) for his excellent web page detailing the knuckle bolt upgrade. I do not know if it is the original but it surely is the defacto standard. The credit for this particular variation belongs to Glenn Miller (jeepngem of earlycj5.com) and to Jim Johnson (jp2flat of earlycj5.com). Without their help my carcass would probably still be out in some remote corner of the desolate Sonoran Desert.*

    Background
    First, some manner of upgrade to knuckle spindle connection is highly recommended. In the original design the spindle connects to the knuckle with 3/8” bolts from the outside. The bolts go through holes in the spindle and thread into the knuckle. The threading into the knuckle is the problem. First the knuckle is cast iron and the threads have been cut into this cast iron lip. Cast iron threads are not as strong and durable as threads in steel. Actually they really suck. The lip were these threaded holes occur is not very thick, so the weak threads are also few. I would strongly suggest reading Vern’s web page on this subject as well as any others you can find so there is a complete understanding of all the minor complexities involved.

    Stock D25/27 Knuckle
    Stock knuckle from a Dana 25/27.

    Button Head Hex Bolt
    This variation of upgrade is based on using a button head bolt. Other upgrades require the use of a particular wheel stud. These wheel studs are not readily available and the source I found wanted about $8.50 apiece for them. At six per side, times two sides, this gets kinda pricey. You may be asking why not a regular bolt? The upgrade requires eliminating the threaded hole and inserting the bolt from the backside. The hex head of a typical bolt would interfere with other moving parts inside the knuckle.

    The button head bolts are more readily available and are reasonably priced. They could be purchased at any well stocked hardware store. The bolt I used I purchased from McMaster-Carr, www.mcmaster.com. They are a good source for many hard to find items. They stock the needed bolt. A box of 25 for about the same price as a single stud. Their part number is 91255A647 for the 3/8-24 NF x 1 1/4” hex socket, button head cap bolt. This is not a cheesy non-graded bolt. It exceeds Grade 5 and conforms to ASTM F835. Just right for this application.

    Modifying the steering knuckle.
    There is simply one thing we need to do to the knuckle for this upgrade. Spotface the backside of each hole. This will give the bolt head a good seat. The castings do vary, but they all have some manner of raised material or boss on the inner wall. Being a casting there are minor variations in the cast surface at each hole location. It is more important that the bolt head have a clean, smooth seat to bear against. This will help to distribute the stresses and therefore give us a stronger connection.

    Clean spotfaces for good bearing surface.
    Clean spotfaces for good bearing surface.

    It may be worth noting that the wheel stud method requires drilling out the threads, spotfacing and inserting the stud into the hole. Being inserted from the backside, the serrated portion of the stud will hold it in place and prevent it from turning while assembling the spindle. These serrations could slightly weaken the casting. When pressed in each serration produces a stress riser and also becomes a likely place for a crack to begin. This button head variation avoids these possible weaknesses. In fact, the threads can remain in the knuckle, we agree they are weak threads but they will help latter during assembly.

    Spotfacing can be done a few different ways. If you have ever done any machining work and are comfortable with this you could do it yourself. Purchase a spotface and chuck it up in your drill press. If you exercise good machine shop practice a quality job will result. I looked into this method and found a spotface with a guide arbor for about $40. If you have no idea what I am talking about you could simply take the knuckles to a machine shop and pay them to do it. It is a simple task for a machinist. I happened to choose a different approach, I called a friend who owns a machine shop and told him I’ll buy lunch. Of course I showed up with knuckles in hand.

    However you choose to accomplish this just remember to remove only enough material to give the bolt head a good seat. Milling a seat much larger than the bolt head diameter is removing unnecessary material and weakening the knuckle. They don’t even need to all be at the same thickness.

    Installed Buttonheads
    Here’s the button heads sitting in their spotfaced seats. Notice the brass bushing in the middle of the spindle. Those streaks are the marks your axle splines makes as your spindle leaves the Jeep!

    Re-assembly
    With the knuckles spotfaced you are ready to install the bolts. By leaving the internal threads in the casting we gain two advantages, a little extra strength and some help in preventing the bolt from turning. Remember when assembling the spindle onto the knuckle the bolt will appear as a stud. In other words, you can’t get a wrench on the bolt head when torquing the nut. Loctite will hold the bolt. While the knuckle is still disassembled (on the workbench), insert the bolts from the backside, use liberal amounts of red (high strength) Loctite under the head of the bolt. Slide the spindle over the bolts, run a nut onto each one and tighten it. This will ensure the bolt head is fully seated and under tension while the Loctite cures, overnight if possible.

    The finished product
    The upgraded-reassembled front axle.

    Carefully re-assemble your steering knuckles and the axles. You know have an upgrade that is an improvement over the factory design.

    Enjoy the confidence of an improved, stronger axle spindle. Happy jeep’in.

    *Editor's note, 'tis true, I saw the whole grisly event in person.
     
  8. Dec 31, 2014
    Rralphs

    Rralphs Old Member

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  9. Dec 31, 2014
    homersdog

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    thanks for info Chuck. I just printed it and will add the hardcopy to my service manual under "things to upgrade"
     
  10. Dec 31, 2014
    OzFin

    OzFin Vintage Jeep Guy

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    Here are a few pictures for you. Oz

    [​IMG]
    [​IMG]
    Some of the bolt heads were turned down for turning clearance purposes.
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    Area to be aware of clearances for full turning abilities.
    [​IMG]
    Checking for full turning abilities.
    [​IMG]
     
  11. Dec 31, 2014
    homersdog

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    Thank you too Oz.
     
  12. Dec 31, 2014
    colojeepguy

    colojeepguy Colorado Springs 2019 Sponsor

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    Thanks Chuck!
    That's exactly the article I was remembering.
    And thanks Oz for the pictures....always a great help.
     
  13. Dec 31, 2014
    wheelie

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    Would an 11/16 spot face bit eliminate, or at least minimize the need for, grinding the heads off those cap screws?
     
  14. Jan 1, 2015
    djbutler

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    Good pictures Oz, you showed exactly what I tried yesterday to describe including reducing the head diameter of the button heads for clearance.

    Wheelie, I wouldn't go larger than the 5/8 counterbore cutter. You see from Oz's pictures that the 5/8 cutter took some material from the sides of the knuckle casting on the two holes at 5:00 and 7:00. I wouldn't want to cut more than that out of the side of the knuckle casting, just cut down the diameter of the button heads to clear.

    Also, the top two threads in each hole will cause the button heads to bind up and not seat all the way down unless you do a clearance cut on the top of the holes. The next set of knuckles I do I'll use a drill a little larger than 3/8 to do this because the drill bit will tend to grab and cut deeper than you wanted to once it gets started cutting. Maybe I'll use a 7/16 and just cut a little bit of a countersink with it.

    Mike, good point about sources for the button heads. I was not aware that Fastenal was selling only Chinese stuff now. I stopped patronizing then because they would only sell minimum $10 to retail customers, when all I wanted was a can of Magic Tap. A little digression on the thread here: Mike, what is the best cutting/tapping fluid on the market now?

    Don
     
  15. Jan 1, 2015
    wheelie

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    Got it Don. I've been mulling over this upgrade for quite sometime. I wasn't crazy about removing that much of the bolt head thinking it would weaken the set up.

    As far as clearancing for the shoulder of the screw, I would think whatever process removes the least amount of supporting material for the screw, would be best.

    Good stuff here folks. I like this subject.
     
  16. Jan 1, 2015
    nickmil

    nickmil In mothballs.

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    Just as a Powerlock fyi. Dana 25, 27, and 30's use the same clutches so if you don't see a listing for 25 or 27 check for the 30 clutches.
     
  17. Jan 8, 2015
    colojeepguy

    colojeepguy Colorado Springs 2019 Sponsor

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  18. Jan 9, 2015
    djbutler

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    Doug,
    I wouldn't spend the money for those. If you look at the bearing caps you will see they have a substantial shoulder that locates into the knuckle that will take any shear force imposed by the vehicle weight. I have never seen any problem with the original cap screws holding the bearing caps in place.

    Don
     
  19. Jan 9, 2015
    Keys5a

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    I studded knuckles for a friend about 5 years ago following the previous procedures. I was not able to find appropriate studs at the time, and substituted studs from Toyota pickup rear drum backing plates. These are 10 by 36 milimeter, slightly larger than the 3/8 by 1 1/4" bolts. The Toyota studs are about .015" larger diameter, and about 3/16" longer. The heads need to be reduced slightly in diameter, but they have nice splines under the head to lock them in.
    These are beefy studs that work quite well.
    -Donny
     
  20. Jan 9, 2015
    colojeepguy

    colojeepguy Colorado Springs 2019 Sponsor

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    OK, that makes sense....thanks!
     

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