The Stovebolt Site Forums The Shop Area Driveline 3/4 ton king pin question

I am going through my 3/4 ton front axle, spindles, etc. and have an issue. The hole in the left end of the axle for the king pin is worn sloppy. I am going to bore and sleeve it, then ream it out to the correct ID. I have a king pin kit from Classic Parts. The pins are .921" OD, and the shop manual says the spindle bushings are to be reamed to .923" ID. My question is, to what ID should the axle hole be reamed to? Is this just an interference fit, or a press fit? I don't want to make the hole too tight and risk galling the pin as it goes through then causing damage to the lower bushing. Since the pin is held firm by the cross bolt, I'm thinking that an interference fit is the right way to go.

Thanks for any input.

Brian

How worn is the axle diameter? Can you measure it? A machine shop should be able to measure it and determine how worn it it. Bushings (steel backed bronze or brass) can take up some slop, 3 to 4 thousandths is acceptable. You might h@ve to go over to th3 ‘wet side’ to get that work done.

Otherwise it would be best to have steel bushings made to get the original ID of the axle for stock bushings.

Ed

If the ID of the axle is worn only a few thousands, you can use Loctite 660 to re-secure the bushings. recommended to me by several forum members, I used it last summer to fill the gap on my king pin bushings that were worn between .002”-005”. So far it is still holding tight. The website says it will fill gaps up to .020”.

Just throwing out another option!

Ed, can you explain?

Thanks. This is exactly what I am proposing to do. But my original question is still out there. What was the original diameter of the hole in the axle? I could just match the hole on the other end of my axle, but I want to be sure that it is correct as well. I can't find a drawing or spec anywhere that gives this dimension. If the king pin is .921" dia., is the hole also .921" (interference fit) or should it be .001" under for a press fit?

Brian

It rails all the time on the coast, thus ‘wet side’ don’t know if you are there or on the ‘dry side?’

Ed

Thanks for the idea. I've used LocTite products for various applications in my line of work. It's great stuff for sure. I'm not sure where you were going with using it to secure the bushings, though. I'm going to install new bushings in my spindles (for a 3/4 ton, the bushings are pressed in then reamed to the correct i.d., vs. a 1/2 ton where they are 'floating'), so that's no problem. The hole through the axle is the issue. Yes, I could clean up the hole and use LocTite to take up the slop around the pin, but to do so, when I install the pin, I'd likely get LocTite down into the lower spindle bushing, too, which would not be a good idea.

Brian

Ha! I get you. Yes, I'm on the wet side of the Cascades, near Mt. Rainier.

I've got a buddy who owns a machine shop nearby. I'm taking the axle to him so I can use his Bridgeport mill (the tilting head will make setting up easy).

Brian

Thanks Ed for the education!

Brian, I misunderstood you question. I was thinking the steering knuckle and not the axle. I’m not sure if you’re aware, but they make oversized king pin kits to address your worn axle where the king pin is secured. This would not require a new bushing to be made but instead just reaming the axle to the oversized king pin. The kit I linked is from Rockauto and is .020” oversized.
[LINK]

I’ll leave the fit to some of the other experts who have done 3600’s but on my 3100 it was a snug fit as I was able to press it in by hand and the tapered bolt secured it further.

I am not a machinist but I think the fit should be such that light hammer blows are needed to install the kingpin. I had hardened steel bushings installed on my 1 Ton axle because of the same problem.

When I had my axle eye ends repaired , the machinist made the fit an firm tap with the HANDLE of the hammer

Sorry to hijack the thread, I have no moment side to side on my king pins but have a little up down (can get about a 20thou feeler between the axle and knuckle) is there a specification for this movement? I can’t seem to find anything

Thanks in advance

Scrap that I just found a manual

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0305.htm

Seems I need to shim as I have a little more.

In case you are not aware, the shim goes on the top side where no weight is placed on it. It's only propose is to take up space.

Thanks mate

All sorted I stripped shims out of an other axle I have we’re all back together with under 5thou in both sides

Caliper mounts fitted and when I throw the axle back under the truck (waiting on rear pins and bushes from Rock auto) I’ll throw the discs and calipers on

Note the COVID Safe grease caps 😂😂