Spindle Bolt Upgrade

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=90 BGCOLOR="#006633" TEXT="#F7F7FF" bgproperties="fixed" background="079005a0ddvuru.png"> <div> <A HREF="http://www.vernco.com/index.htm" TARGET="_top" TITLE="http://www.vernco.com/index.htm"><U><B>home</B></U></A><B>     |     </B><FONT SIZE="5" COLOR="#FFCC66" FACE="Arial" ><B>Vern</B><B>co.com</B></FONT></div> <div> back to<B>  </B><A HREF="index.htm" TARGET="_top" TITLE="Front Axle Rebuild"><U><B>Front Axle Rebuild</B></U></A></div> <bR> <div> <A HREF="http://www.vernco.com/id173.htm" TARGET="_top" TITLE="http://www.vernco.com/id173.htm"><U><B>Site Map</B></U></A></div> <div> </div> </td> </tr><tr> <td valign="top" width=150 BGCOLOR="#669966" TEXT="#080000"> <div> <A HREF="id372.htm" TARGET="_top" TITLE="Front Differential and Housing"><U>Front Differential and Housing</U></A></div> <div> <B>Spindle Bolt Upgrade</B></div> <div> <A HREF="id373.htm" TARGET="_top" TITLE="Kingpin Bearings"><U>Kingpin Bearings</U></A></div> <div> <A HREF="id374.htm" TARGET="_top" TITLE="Bendix Joints"><U>Bendix Joints</U></A></div> <div> <A HREF="id460.htm" TARGET="_top" TITLE="Spindles, etc."><U>Spindles, etc.</U></A></div> <div> <A HREF="id461.htm" TARGET="_top" TITLE="Hubs and Drums"><U>Hubs and Drums</U></A></div> <div> <A HREF="id495.htm" TARGET="_top" TITLE="Front End Alignment"><U>Front End Alignment</U></A></div> <bR> </td> <td valign="top" height=390 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> The stock means of attaching the front spindles leaves much to be desired.  Six bolts thread into the cast iron spindle.  I'm no expert on metals and fasteners, but I do know that female threads in cast iron are significantly weaker than the mating bolts.  Don't be surprised to find these bolt holes stripped from many years of being overtorqued and other abuses.  I'm no lawyer, and don't even play one on TV, but your easiest repair for stripped threads is to replace the knuckle.  Should you choose to undertake this upgrade, the quality workmanship needed cannot be overemphasized.  If you are not comfortable doing the work yourself, find a competent machine shop.  While not difficult, this isn't the type of job to do out in the driveway with a hand drill, a big hammer and a 6-pack of beer.  (Nor is the answer more beer, such as a 12-pack or a case.)</div> <bR> <div> With that quasi-legal reminder out of the way, let's take a look at one method to improve the situation.</div> <bR> <div> This picture shows the six stock bolts that thread into the knuckle casting.  The brake backing plate is not shown for clarity:</div> <bR> <div> <A HREF="id405.htm" TARGET="_top" TITLE="Stock Spindle bolts"><U><IMG SRC="66f964d0.jpg" border=0 width="150" height="77" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> Here is what I found on my axle.  Two of the six bolt holes were completely useless.  One was fully stripped, and a second was almost gone, too.  The remaining bolt holes showed minor signs of thread damage.  If a spindle were to separate from the knuckle, the results would be catastrophic.  The bolt holes are too close to the inner edge for any type of Heli-Coil repair.  A Heli-Coil is a strong, permanent repair but requires drilling the hole oversize.  There is simply not enough material adjacent to the inner edge for this:</div> <bR> <div> <A HREF="id406.htm" TARGET="_top" TITLE="Stripped Knuckle Threads"><U><IMG SRC="6717d4a0.jpg" border=0 width="125" height="74" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> These bolt holes can be inspected on the vehicle without too much disassembly.  The next time you have access to the front brakes, remove a single spindle bolt at a time, keeping the other five bolts in place.  If the bolt holes have recently stripped, you will see metal wrapped around the bolt threads.  With a bolt removed, carefully inspect inside the bolt hole with a bright flashlight.  Should you find any damage, do NOT drive the vehicle until repaired.</div> <div>  <A NAME="where_to_buy"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A></div> <div> Luckily, the upgrade is not too hard to accomplish.  Instead of bolts that thread into the knuckle, the threads are drilled out and studs are pressed in from behind.  The studs are Mopar part number J8124847.  Among other applications, they were used to secure the spindles on 81-86 Cherokees.  Shop carefully when calling Chrysler dealers, as I was quoted various prices between $2 and $6 each.  These parts arrived in a box with the Spicer part number 6-8124847.  That is the same base number but with a different prefix.  Any vendor who carries Spicer parts should be able to order them for you.  Here is the finished knuckle:</div> <bR> <div> <A HREF="id415.htm" TARGET="_top" TITLE="Studs installed view from spindle side"><U><IMG SRC="6737d500.jpg" border=0 width="125" height="80" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> August 2004 Update: I've received many queries about where to purchase these studs.  I ordered them, perhaps in late 1999, from <A HREF="http://www.wilsons4x4.com/" TARGET="_blank" TITLE="http://www.wilsons4x4.com/"><U>Wilson's 4x4</U></A> in Holly Hill, Florida.  Feel free to contact them, but I do <B>NOT</B> know if they still carry them.  For another source, visit <A HREF="http://www.jeepdoc.com/default.asp" TARGET="_blank" TITLE="http://www.jeepdoc.com/default.asp"><U>Krage Motorsports</U></A> and enter "8124847" (No prefix) in the Search box.  </div> <bR> <div> I recently did the same upgrade on my '51 Willys wagon and picked up the studs from my local branch of <A HREF="http://www.sixstates.com" TARGET="_blank" TITLE="http://www.sixstates.com"><U>Six States Distributors</U></A>.  The part number on the Dana/Spicer box is now 36326-2.</div> <bR> <div> There is a potential problem with the added thickness of the stud heads.  Before you start drilling away, look at this picture of the completed knuckle in a sharp turn.  The stud head at the 9:00 position is hitting the ball end.  The 3:00 stud head will hit in the other direction.  The 5:00 and 7:00 studs will also require a teensy bit of rework for clearance.  Please note that the next two pictures show temporary bolts used in place of the <A HREF="id373_kingpin_bearing_cap_studs.htm" TARGET="_top" TITLE="Kingpin Bearings"><U>kingpin bearing studs</U></A>:</div> <bR> <div> <A HREF="id409.htm" TARGET="_top" TITLE="Studs hitting ball end"><U><IMG SRC="6757d5e0.jpg" border=0 width="125" height="94" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> Because of the interference, others who have done this modification have recommended to keep the stock bolts at the 3:00 and 9:00 positions.  That is an excellent idea, but those bolt holes were damaged on my axle.  Depending on what type of axleshafts are used, this may not be a problem.  The manual specifies a maximum turn angle of 23 degrees for my <A HREF="id374.htm" TARGET="_top" TITLE="Bendix Joints"><U>Bendix axleshafts</U></A>.  This gave me just enough clearance for the stud heads after a little bit of rework.  Other types of axleshafts can turn further, so the 3:00 and 9:00 studs cannot be used.  In that case, the knuckles would have to be replaced.  Should you need to replace the knuckles, check out a picture showing a problem with some reproductions at <A HREF="http://www.jeep-trucks.com/WOJP/Steering/index.html" TARGET="_blank" TITLE="http://www.jeep-trucks.com/WOJP/Steering"><U>David Hoelzeman's website</U></A>.</div> <bR> <div> Before doing anything with the knuckle casting, check the travel and see how much clearance is present for the stud heads.  To check the travel, an easy method is to rotate the axle with the driveshaft yoke pointing straight up.  Rest the mounting surface for the differential cover on wooden blocks.  With the axle on the face like that, use an angle finder to check the travel.  Make sure you shim the axle level so you are measuring the angle accurately in each direction from a neutral point.  Note how the turn limit stop won't touch until the knuckle seals are installed.  However, we are not checking the turn limit stop adjustment at this point.  We are checking for clearance for the stud heads inside the knuckle.  I needed 23 degrees of travel, and had 25 degrees in both directions before the stud heads hit.  When the knuckle seals are installed, the <A HREF="id373_turn_limit_with_seal.htm" TARGET="_top" TITLE="Kingpin Bearings"><U>turn limit stops</U></A> will be set for the specified 23 degrees.  The studs are already installed in this picture:</div> <bR> <div> <A HREF="id411.htm" TARGET="_top" TITLE="Angle finder on knuckle no seal"><U><IMG SRC="6baaf370.jpg" border=0 width="175" height="55" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> To mock up the thickness of the stud heads, I found a bolt with a head of the same thickness.  Since this is a 5/16" bolt, it slips easily from inside the knuckle into the threaded 3/8" hole.  This let me swing the knuckle and see how the stud head would hit.  Note the serrations on the stud which will keep it from rotating when installed:</div> <bR> <div> <A HREF="id408.htm" TARGET="_top" TITLE="Mopar stud and test bolt"><U><IMG SRC="6797d500.jpg" border=0 width="125" height="80" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> It was helpful to lightly clean up the edge of the axlehousing ball ends.  Don't touch the ball end at the 3:00 or 9:00 positions, as any grinding there will interfere with the knuckle seal.  At the 5:00 and 7:00 positions, I took off less than 1/32", which was little more than cleaning up the rough edges of the ball end casting.  Because of the close proximity to the pivot point, that small amount made a big difference in the travel of the knuckle.  No extra clearance was needed for the 11:00 or 1:00 positions:</div> <bR> <div> <A HREF="id416.htm" TARGET="_top" TITLE="Knuckle relief on ball end"><U><IMG SRC="67f964b0.jpg" border=0 width="150" height="75" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> Update: While performing the same upgrade on my '51 Willys wagon, it was not possible to use studs at the 11:00 and 1:00 positions.  The knuckle walls had a different shape there, leaving no room for the stud heads on the inside.  The existing threads at the 3:00 and 9:00 positions were fine and were left alone as previously recommended.  The 5:00 and 7:00 positions, which would appear to be under the greatest stress due to the action of the vehicle weight, were the only ones modified.</div> <bR> <div> The inside of the knuckle is a rough casting with a raised boss for each bolt hole.  Rather than grind down the stud head for clearance, clean up the casting instead.  This will also provide a smooth surface in full contact with the stud head for a stronger overall assembly.  The taper of the rough casting would put an uneven force under the stud head and lead to an early failure.  This picture shows the difference between the rough cast bosses and one that has been machined:  </div> <bR> <div>    <A HREF="id407.htm" TARGET="_top" TITLE="Mopar Studs"><U><IMG SRC="67b7d2d0.jpg" border=0 width="125" height="45" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> How much to clean up the bosses is a critical decision.  The 5/16" test bolt I used showed where the stud heads would hit.  By grinding down the test bolt head, I learned how much extra clearance was needed for full travel.  I ground the 5/16" bolt head way down, and then stacked washers under the head for easier adjustments.  A stack of washers by themselves could be used, but it was much easier to hold them with the ground-down bolt.  I measured the combined thickness of the ground-down test bolt, washers, and the rough cast boss.  This showed the total maximum dimension allowable when the full thickness stud head would be installed.  From that dimension, I subtracted the thickness of the stud head, resulting in the desired thickness of the machined boss on the knuckle.  </div> <bR> <div> In this picture, the thickness of the boss is being checked after the machining operation.  In my case, .390" worked very well and required little more than skimming the tops of the cast bosses.  Since there will be variations in castings, take the time to confirm what finished thickness you will need:</div> <bR> <div> <A HREF="id410.htm" TARGET="_top" TITLE="Measuring boss thickness"><U><IMG SRC="67d7d4c0.jpg" border=0 width="125" height="76" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> A drill press and counterbore will make quick work of the machining.  Select a counterbore with an outside diameter of 5/8" to match the heads of the studs.  If you go larger than that, the edges of the cutter will hit the inner wall of the knuckle.  The only 5/8" counterbore I owned had a 5/16" pilot, which was too small for the 3/8" finished hole.  While scratching my head, I noticed the 5/16" pilot fit perfectly inside the existing 3/8" threads.  So should you need to use a 5/16" pilot like I did, do the counterbore operation first:</div> <bR> <div> <A HREF="id412.htm" TARGET="_top" TITLE="Counterbore on knuckle"><U><IMG SRC="68196550.jpg" border=0 width="150" height="85" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> Counterbores are also available with separate interchangeable pilots in a wide range of sizes.  To purchase a counterbore, <A HREF="http://www.mscdirect.com" TARGET="_blank" TITLE="http://www.mscdirect.com"><U>MSCDirect.com</U></A> is one good source.  MSC #08790404 is a counterbore that fits a 1/2" diameter drill press chuck and has a 5/8" diameter cutter.  Order MSC #08904245, a 3/8" diameter pilot to go with it.</div> <bR> <div> After the counterbores were cut to the correct depth, the threads were drilled out to the final 3/8" diameter.  Remember, although I made do with the tooling I had, it is preferable to drill out the threads first, followed by a counterbore with a 3/8" diameter pilot.  Note the small C-clamp holding the knuckle on the drill press table:</div> <bR> <div>  <A HREF="id413.htm" TARGET="_top" TITLE="Drilling knuckle"><U><IMG SRC="683965a0.jpg" border=0 width="150" height="90" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> After the counterboring and drilling is done, it is vital to deburr the sharp edge to prevent future cracking.  (Warning:  Sarcasm ahead)  If you'd prefer to skip this step, please leave the lugnuts off after installing the wheels on your Jeep.  That way, your wheels will fall off before you reach the end of your driveway and nobody will get hurt.  (End of Sarcasm)</div> <bR> <div> Now for the moment we've all been waiting for, installing the studs.  The arbor press would have worked just fine, but the <A HREF="id460_arbor_press.htm" TARGET="_top" TITLE="Spindles, etc."><U>fracture</U></A> that I brazed back together was making ominous sounds, so I used a brass-faced punch in the trusty air hammer.  Another trick is to pull them in place with a nut and washer.  Use the spindle as a guide to ensure the studs go in straight.  The spindle flange is resting on the padded jaws of a vise for support.:</div> <bR> <div> <A HREF="id414.htm" TARGET="_top" TITLE="Airhammer on studs"><U><IMG SRC="6857d6e0.jpg" border=0 width="125" height="110" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> I don't believe it was ever used from the factory, but before installing the brake backing plate, add a thin paper gasket or sealant between the spindle and knuckle to retain the lube.  </div> <bR> <div> I'm partial to all-metal Gr. 8 locking nuts for an application like this.  Don't use Nylon insert locking nuts as they can be damaged by the heat from the brakes. </div> <bR> <div> Click <A HREF="http://www.oldjeep.com/disc.htm" TARGET="_blank" TITLE="http://www.oldjeep.com/disc.htm"><U>here</U></A> to visit Chuck Pedretti's website where I learned about this upgrade.</div> <bR> <bR> <bR> <bR> <bR> <bR> </td> </tr></table></body>