King pin play in the axle hole

[mrtexas]

I was putting in different king pins today and noticed that without the locking bolt there was quite a bit of play in the fit of the kingpin in the axle hole. With the locking bolt in the kingpin fits tight.

Is this a problem?

[MikeK]

Despite the lock bolt being tight and everything seemingly solid, the pin will rock some in the hole under the heavy load of road bumps while driving. The fix would be boring and pressing steel sleeves in the axle. Lots of truck axles get fixed that way if oversize pins are not available.

[Ron in Quincy]

One of our members just found the same problem when rebuilding his A front end.

As MikeK said, ream out the axel and install a sleeve so the Spindle bold (king pin) fits snug, but turns freely so steering is smooth.

Ron

[kenparker]

I am in the process of repairing that problem right now. I am replacing the axel with one that does not have a worn Out of Round hole.
The locking pin worked itself loose and the rocking motion of hte king pin wore the hole in the axel about 20 thou out of round. The front end wobble was terrrriiible.
Strangly enuff the bushings in the spindle are not at all worn - but will replace everything just to be safe.

[Glenn C.]

Many axles in our local club have had the king pin to axle boss fit restored by first checking to see that the axle is straight, not twisted etc. The pin hole inclination is correct. Once all this has been done, the axle king pin boss is heated to cherry red, and shrunk closed a few thousands of an inch. A spiral reamer is then used to re-size the king pin bore in the axle end. Our club members have used this technique for the last +30yrs with no complaint.

[Jason in TX]

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Originally Posted by Ron in Quincy

As MikeK said, ream out the axel and install a sleeve so the Spindle bold (king pin) fits snug, but turns freely so steering is smooth.
Ron

The king pin does not turn. Hence the locking pin, and also the cup that the brake shaft mounts to. All that does not turn.

The locking pin that is pushed through the shaft will drive the king pin to the outter ends of the axle, and the kingpin will stay put if that locking pin is tight. This is not a wear area because the kingpin does not rotate and wear out the axle.

Now, with that said, Like KenParker's problem above, if the locking pin had been loose for years of driving, and the axle was damaged by movement of the king pin, then you have another story. If your king pin is just barely moving (you said it was tight with the pin) then make sure your spindle bushings are reamed and tight, and then enjoy the ride. You will be fine.

[Paul from Maine]

Originally Posted by Ron in Quincy

One of our members just found the same problem when rebuilding his A front end.

As MikeK said, ream out the axel and install a sleeve so the Spindle bold (king pin) fits snug, but turns freely so steering is smooth.

Ron

Are you saying the King pin should rotate?

[Jason in TX]

King Pin Should NOT rotate.

[MikeK]

Originally Posted by Jason in TX

The king pin does not turn. Hence the locking pin, and also the cup that the brake shaft mounts to. All that does not turn.

The locking pin that is pushed through the shaft will drive the king pin to the outter ends of the axle, and the kingpin will stay put if that locking pin is tight. This is not a wear area because the kingpin does not rotate and wear out the axle.

Now, with that said, Like KenParker's problem above, if the locking pin had been loose for years of driving, and the axle was damaged by movement of the king pin, then you have another story. If your king pin is just barely moving (you said it was tight with the pin) then make sure your spindle bushings are reamed and tight, and then enjoy the ride. You will be fine.

You will not be fine, steering will suffer, the problem will get worse.
In an oversized hole, that lock pin acts as a pivot point no matter how tight it is. The king pin flexes and rocks under heavy load. You do not need rotation for wear to occur. The metal gets hammered, or forged out of shape.

Once the hole is slightly oversize, you no longer have full surface contact to distribute the pressure, only line contact that concentrates it. That line contact exceeds the compressive strength of the steel and moves metal. The king pin will rock in the direction opposite the side of the hole it is clamped to, toward that oversized clearance, and hit it with line contact.

No matter how tight the taper pin is, no matter how solid it feels by hand, an oversized hole will quickly lead to that hole camming out into an hourglass shape, with the pin still clamped tight at the center of the hourglass. The car will drive like it has worn axle bushings, despite the bushings being new and tight.

[RichPA]

A lot of these axle "eyes" become that way because someone drove a "mushroomed" kingpin out with a hammer and drift instead of a press. An easy fix is to heat the eye red, hold an old kingpin in place in the eye and shrink the eye around the pin with a hammer. I learned this years ago from an old timer.

[Ron in Quincy]

SORRY PEOPLE, i DIDN'T MEAN THE KIN PIN TURNS FREELY, MEANT THE SPINDLE ASSEMBLY TURNS FREELY AFTER THE KING PIN IS LOCKED IN THE AXEL PROPERLY.

SORRY FOR USING A POOR CHOICE OF WORDS !!!!!!!!!

RON

[295W]

I know this is an old thread, but I have a used axle and a new kingpin set and the kingpin seems very tight going into the axle - like it would need to be driven into the axle. I had someone tell me to clean it up with sand paper and a dowel - there does seem to be some dirt, paint etc. in the holes but I do not want to ruin the axle - though I guess if it became too big (unlikely) it could be machined and sleeved .... Any suggestions on how to best do this - Im a bit of a newbie are there different kingpins for different axles - I can not id the axle but do know the spindles are aftermarket 37-41 ??? Thanks!

[Tom Wesenberg]

You can make a sander for small holes by taking a 10" piece of 1/2" wood dowl and cutting a slot in the end about 1" deep, right down the center. Take a strip of sandpaper about 1" by 8" long and fold it in half with the rough side out. Tuck it into the slot and wrap it around the dowl in the same dirrection the drill will spin it. Go up and down the hole the same way you'd hone a wheel cylinder. I've been doing this for many years to clean out small holes.

[KR500]

When I have been told of a loose king pin in axle, my first question is "What is the actual diameter of the replacement king pin" Many repro king pins measure .811 in diamter not .8125