Technical 51Chevy Truck front axle

Howdy all, recently picked up an AD truck which prior owner had already taken apart... Went to put the front axle on the springs and it appears the alignment pin hole right side in the axle is smaller than typical. No issue on the left side. All my mopars had IFS so I’m new to beams, what am I missing?
Thanks

 

Pic of your issue would help. Are you talking about the center bolt in the spring?

Edit.: if so, does the locating hole in the pad need to be cleaned out?

 

Yes center spring bolt mating hole. cleaning it was my first thought but appears to be metal.. There’s a set of two holes each identical size. You can see in the image where I scraped to bear metal at the pin diameter.

 

Isn't the second hole for the factory shim plate, not sure why the spring hole is smaller than the other side, should be the same size left to right.

 

I’ve seen the spring bolt get banged up or a wrong size used for a repair.
Check it.
Compare size from side to side.

 

Looks to be 9/16” dia, seem correct?
Hole in the axle left side was noticeably larger

 

I should clarify the spring pin are 9/16

 

9/16 Sounds too big but I'll go out and measure.

 

There is a spring wedge that has a tab on the back to keep the axle at 7 degrees, the spring wedge has a hole for the bolt in the spring pack

 

random pic.
I have a 49 gm truck axle set up outside. I can take a pic tomorrow if ya need it

 

So that spring wedge is right side only then? Thanks to everyone for the responses

 

Spring wedge is on both sides

 

No. Both sides have something
I’ll take a pic tomorrow

 

I can get some pics of my sons axle if needed. It is just out in the shop and has no front clip on it so easy to see.

 

But, sounds like the spring pin is bigger than it should be. Pretty sure those are typically a 3/8” bolt which I suppose might have a 9/16” hex head if they used a normal bolt.

 

If there’s pics I’d be interested to see if the axle holes match what I’m seeing. Thanks

 

Here is my 49 axle

not much help

 

I see the shim in that stack but have a hard time believing it’s enough to take up my leaf pin height. Thanks for the pic
I know the springs that came with the truck were rebuilt so it’s not unlikely that’s some of my issue

 

Mine has knee action shocks. If your has modern style tube shocks your set up could be different

 

That center bolt hole looks like it’s rusty in there. I could check the size on a ‘55-9 front axle, but since it seems you’re now installing an axle, put a drill bit in the other side, see if it fits the side you’re having issues with.
Ie if it’s 9/16th, then use the bit by hand to clean up/out the hole.

 

Yep I can open up the hole but was concerned I’m overlooking a reason it’s smaller by design.

 

I have never seen this on an AD truck, but it has been a common industrial practice to make assemblies such that they cannot be installed incorrectly.

The practice is calle poka-yoke. It is a Japanese term that means "mistake-proofing" or "inadvertent error prevention". A poka-yoke is any mechanism in a process that helps an equipment operator avoid (yokeru) mistakes (poka) and defects by preventing, correcting, or drawing attention to human errors as they occur. The concept was formalized, and the term adopted, by Shigeo Shingo as part of the Toyota Production System.

 

That was my first though, it was to preclude reversing the axle for caster reasons but seems that’s by shims. Your comment you haven’t seen it on AD also led me to wonder if it’s just the wrong axle but kingpin width at least seem to check out. Hopefully its just rust. I plan to send to Sid’s for a drop so if it’s wrong I’m sure he’ll know… this at least answers my question that I shouldn’t be seeing it on the AD
Thanks everyone

 

I didn’t mean to say open it up, but to just clean it out with a bit by hand, not in the drill.
One other thing, did you measure te “head” of the spring bolt and compare to the other one?

 

We always just called it idiot proofing. But the problem is they keep making better idiots.

 

I didn’t get a chance to measure yet but the hole diameter difference in the axle was enough to see by eye as it was way different left to right.

 

Spring wedges are not a factory thing, and you don't necessarily need a wedge at all. So don't go putting wedges in unless kingpin angle determines you need them.
The centering bolt size is 5/16" fine thread, and the head may be 9/16", but not the bolt. I usually buy 5/16" Allen cap bolts as the heads fit the axle hole fine, and the bolts fit the springs. If one of your holes is larger, it's possible someone changed the centering pin with a pin that had a larger head, and drilled out that hole. Likely the smaller hole is the correct size, and never got opened up.
The axles are not hard material, and it's easy to drill the hole to fit the head of the pin; but you can also clamp the spring pack to keep it compressed and change the pin out to an Allen head and fix it that way also.
These axles aren't complicated, and there's more than one way to fix this. Over 70 years a lot have been changed, so never know what you'll find when working on one.