View Full Version : Front Axle: KingPin and Knuckle "shim /clearance" setting procedure; knuckle won't sit flush on kingpin

09-17-2017, 12:08 PM
Interesting and puzzling observation yesterday while assembling my kingpins & knuckles.... I noticed in trying follow the Shop Manual's "pre-set" procedure for "how may shims on the knuckle?", that my knuckle would NOT seat all the way down on the kingpin. I have NOS Kingpins, both still had Stude factory tags on them, but I had my old kingpins there so also tried them in case my NOS ones were from a 'bad machining day' at the factory. But the knuckle wouldn't go all the way down on them either; there is a slight radius at the bottom. As there logically SHOULD be for machining, wouldn't want a dead sharp there. Shims were same; they would NOT sit flush on the knuckle face either. About 0.012" feeler gauge took up the slop, but certainly a lot more than the Manual's spec for clearance. So, if the knuckle doesn't sit flush to begin with against the kingpin flange, I could not do the 0.006" feeler gauge method, as there was already MORE gap than this.

The thrust bearing has a little recess at the inner radius, and so THAT fits better and is what will sit in that position later ANYWAY (again, these are the original Stude parts, OR my NORS NAPA parts, and both sets of kingpins, using my original knuckle), and so I simply put the bearing and shims on as they WILL be; thrust bearing on the bottom (kingpin is upside down in the vise, remember), then the shims, then the knuckle. THEN put the feeler gauge between the shims and knuckle; THIS allowed me to look at the top of the KNUCKLE and get it flush with the noted shoulder/step of the Kingpin.

I think I'm set up OK now with intended 0.006" clearance; but I'm very curious about the Shop Manual procedure, considering that radius. It WOULD work if the bushing were pushed in past flush, but from all accounts the bushing is supposed to be pushed in 'flush', not deeper than that (which WOULD allow some clearance around that taper in the base of the kingpin). So, how could anyone possibly follow the Shop Manual's method? Unless you push that bushing in another .010-.015", CAN'T ever get flush with the face of the kingpin flange or shoulder.

Has anyone else noticed this, or WERE the bushings always pushed in a little past flush at the factory, which would allow for this? It seems just as good if the procedure were to stack the pieces all up as USED, and make sure the knuckle is flush with the shoulder on the kingpin. And if not, lift the knuckle off and add/remove a shim.... Very curious, as that radius HAS to be there, you can't have a dead-sharp there or the king pin wouldn't be as strong, so this had to be an issue IF the bearing is flush in the knuckle. I was going to push the bushing in a little deeper so I could follow the manual, but then figured WHY, it's only for a measurement, and I can just stack the pieces in a different sequence and get my spec clearance of 0.006".

Just seems strange, and wonder if anyone who had the luxury of using the real Stude tools for installing bushings and bearings in the knuckle knows if that bushing in the knuckle WAS pushed in a few thousandths past flush?? Or remembers from looking at original factory knuckles? (not just for this shim-setting procedure, but maybe they did it to allow for, .... who knows what?). Of course, ONE thing I don't have photos of that would show that detail before I disassembled my knuckles (ie: pushed the old bushings out) ;-)

09-17-2017, 12:31 PM
Ok, now I am utterly confused. The thrust bearing has a radius on its inner diameter and that matches with the radius between the flange and the shank on the kingpin. It goes on first. Then comes the knuckle with its bushing and bearing. Because of the thrust bearing being already there, the bushing and bearing are presented with nothing but nice straight diameters to ride upon. The knuckle never comes near the flange or its radius. Perhaps I misunderstand your dilema.

09-17-2017, 12:37 PM
I'm like Ross, not sure I understand. A pic or two might be helpful.

09-17-2017, 02:16 PM
Sorry, my point was simply "why does the Manual's procedure" for setting the knuckle's clearance have you putting the knuckle on the kingpin FIRST, when it won't fit over that radius? I DID end up " setting clearance " by simply assembling with the thrust bearing in its normal position. Why doesn't Studebaker shop manual? I'd ignore, except I've learned the hard way the manual is rarely wrong.....

Steve Winzar
09-17-2017, 09:14 PM
Hi Bsrosel- Your second paragraph is correct procedure- you are on the right track. I found my bronze bushings had been not fully seated by the previous owner so I licked them with a file- now they're flush(you could conceivably press these in a bit further but a file sorted it out!). The procedure recommended to me is as follows (forget the book for now).
Install your knuckle with No seals, NO shims and the bolt your Stand in place firmly.
Now measure clearance between the Knuckle and the face of the Stand. (Note: dress this face with a few stokes of a file before you commence as it will take off any asperities or bumps)
Disassemble and add your Shims accordingly; they go in between the bottom of the thrust bearing and the top of the knuckle.
Recheck the assembly with the Kingpin but tightened again
This procedure worked well for me and doing this showed up flaws in the previous setup that actually changed the shim requirements.

09-17-2017, 09:45 PM
Thanks Steve,
yes, did push the bearing down a tad, to get that O-ring to sit a little lower. Looks good. And we are on the same page with getting everything "flush" for measuring. (still wonder why manual would have knuckle on first, against that tapered shoulder.... oh well).

ONE QUESTION for you; what are you tightening down? Are you actually forcing that nasty "support" with key onto the spindle, tightening that down (without O-ring) to make a final clearance check with a feeler gauge? And then having to knock it off again with a hammer? (at least it was a real bugger getting it off originally, and it barely goes on now, going to take a good whacking to get it to where I could thread the nut on and force it the rest of the way. Certainly had not planned on doing it TWICE. :-) But IS that what you actually are doing, or am I missing something? I'm not sure what ELSE you could be tightening down, except the actually "support" with the keyway. If so, did you get any differerent measurement than you intended (0.006") when you simply stacked the bearing, shims and knuckle (on feeler gauge) and leveled/eye-balled to the shoulder edge on the king-pin? Thanks!

Steve Winzar
09-18-2017, 01:54 AM
Barry- I hope the Kingpin Support is not already attached to anything else because it will be hard to manage if it's on the Control Arm. But yes, I used the big nut and washer to tighten it down onto the end of the Kingpin and measured the Clearance between Support upper face and Knuckle lower face without seals and NO Key (forgot to mention that earlier). BTW the Support should NOT be a hard fit onto the Kingpin. If you are having difficulty here I'm surprised, so a little judicious rub with abrasive cloth might be an idea. It sounds like you are doing everything right. I ended up with.004" clearance on both suspension sides.

09-18-2017, 09:58 PM
No, have not connected ANYTHING yet, I'm slow to start, over-analyze perhaps, but cars are a hobby for me, thank goodness, not getting paid by the hour or my family would have died of starvation years ago!

ah, yes, no need for the doggone key at this point; that would make it easier (assembly and dis-assembly).
I have NOS kingpins, so the ends are virgin, but I've not tried very hard (or put any oil on) to put the lower support on, either. It will be much easier without the key, and you are right; this IS the only way to really be positive what the clearance is, all things considered. Worth the little bit of extra effort considering wanting to be able to grease it AND not have it bind. You did a good job prepping it if you wound up with 0.004" on each side! I'm impressed!

Steve Winzar
09-19-2017, 09:17 AM
Thanks Barry, Ir's not really difficult, especially if you have a range of shim thicknesses available to you. You can even rub the ends of the knuckle on a sheet of Emery paper if you need to sneak up on a bit of clearance.