The Stovebolt Site Forums The Shop Area General Truck Talk 49 1/2ton kingpin help

Hi all, i replaced the kingpin on one side today, i have a question (i've never replaced kingpins before so...)What is stopping the bottom kingpin bushing working its way down and dropping out, due to vibration. It didnt need pressing in, but it is not a very sloppy fit, the bottom dust cover (welch plug i think you call it) just taps in, so isnt meant to hold the bushing in. Do i need either oversize bushings or new spindle/steering knuckle, or have i missed something. The old bushing needed tapping (hard tapping) out..
Any help is appreciated. I should add, with it all together the spindle/steering knuckle feels good with no play....but that bushing is niggling the back of my mind

The 1/2 ton king pin bushings are floating bushings. They do not need to be pressed-in; however, they should not "wobble" when in place. If you have almost no wobble (just up-down movement), you are most likely OK.

Over-sized bushings are for over-size king pins. You need over-size king pins if the king pins wobble in the holes in the axle. Did you test-fit the king pins in the axle before reassembly? How tight were they?

I would say that the new kingpins in the axle passed through easily with very very slight wobble, the bushings would move up and down and swivel around very easily but no real wobble when in place in the spindle, thats why i dont see how they wont vibrate down? With it greased up and all together there is no wobble. hope that makes sense?

If you have any wobble, kingpin to axle, that is a problem. The lock bolt will mask the problem during assembly but it lossen up with driving. Ask me how I know!

The freeze plug type cap retaines the bushing from working out. Put it in & hammer it in the center to spread it. The center punch a few places in the spindle close to the plug. That will hold it in but grease it slowly so the pressure doesn't blow it out.

Mmmm, I think in that case as you say the lock bolt has masked the problem, very frustrating as being in the UK the shipping costs and the time it takes. Anyway this is meant to be enjoyable, i must learn to enjoy the downs as well as the ups! Thanks for all your input guys.

Johnny,

The looseness in the king pin might cause the bushings to wear more quickly and/or cause the bushings to slam against the journals in the knuckles. Wallowed-out bushing journals are are a common and almost tragic situation. When/if that happens, you are SOL. Replacement knuckles that are in good shape are hard to find.

Thanks for the useful comments. If i decide to try oversize kinpins are outside diameter of the bushings also oversize, or is it just the kingpin which is over and in turn the internal diameter of the bushing. SO when the knuckles are too worn what do we do then?

You are correct in your understanding.

When the knuckles are wallowed out, you are SOL.

It would be nice if someone posted a MOOG part number for a set of bushings that are a little oversized.

I would first bolt a tire and wheel on---forget the bottom plug and with it jacked up grab it by the top and bottom of the tire and wiggle. If no or a very tiny amount of play your fine. If a bit more wiggle have a helper watch the bottom of the king pin/bushing and see if the bushing moves at all in the knuckle bore. If it does it's no big deal if you know a competent machinist. We clamp them up on our vertical mill and bore them to 0.050 oversize and then ream them to 0.060 before then using the Sunnen to hone them to exactly 0.0625 or 1/16". A bushing is turned on the lathe so the OD is correct for the knuckle and the ID is 0.002 under and then reamed to exact size AFTER its pressed into the knuckle. After cleaning with acetone the new reducer is pushed into place with Sleeve-Lok on the knuckle surface. Only heat can now remove it. The bore in the knuckle has had a total of 1/8" of metal removed but they were designed for rough roads and heavy loads so never had any trouble yet. We usually touch up the shoulder where the welch plug goes if it's been punched several times but I have seen a number of them held in place with a dot of weld on each side. We only do this for our own in house projects so I have no idea what it would cost at a regular machine shop.

Good info there coilover, thanks.
Thanks to all who posted, all very useful information..Il be posting again soon!