New king pin a hair too big - what to do?

[motoMark]

Hello all,

I'm in the process of replacing the king pins and bushings on my 51 Cambridge and found that the new king pins are too big, by about 0.005", to slide through the support. The old king pins measured 0.7945" and the new pins I purchased in a kit from AB measured 0.800". I never thought to check the fit of the new pins in the support before I took the knuckles to the machine shop to have the new bushings installed and reamed. But now the new bushings are reamed to fit the new pins and I can't get the pins in the support.

 

So I guess I have 2 options. 1st one is to re-use the old king pins, which are in pretty good shape, and live with a little extra clearance with the bushings. Or number 2, hone the holes in the supports to accommodate the new pins, thus having the proper clearance with the bushings.

 

Any thoughts?

[Sniper]

Interesting, when I had the machine shop redo my king pins I just took the the kit, ACDELCO 45F0025, to them and had them do it.  They reported no issues and it's nice and tight.  But I too them the upright and the spindle, as an assembly, and had them fit it up.

[D35 Torpedo]

And here I thought I could replace them in an afternoon. Sounds like i will need to buy a reamer.

[Los_Control]

Seems not a lot of info on these old mopars ..... we might need a video of @keithb7 replacing king pins ...

 

Same time the videos I watch like iron trap garage shows replacing king pins on old Fords.

They do not fit out of the box, you either need to ream out the axle or the spindles .... just saying you need to fit them to  your needs.

 

They are oversized so they can be machined to fit.

 

King pins really do need to fit precisely, .... If you can get any movement in your spindles 1/16th of a inch .... they are shot & should be replaced.

 

Yes you can do it, not really a afternoon job for the first timer. ..... I doubt I could do it ever.

 

 

[47 dodge 1.5 ton]

Make sure you get a reamer that locates in the adjacent pin to get a good job. Not bad to do, you will need a intra mic or telescopic gauge and OD mic to get a measurement. 
  Factory calls for an interference fit .0005” for my truck, might be the same for you.  I made mine +.0002” clearance so I could shim correctly.

Edited March 18, 2023 by 47 dodge 1.5 ton

[Plymouthy Adams]

Anytime you take an item to a machine shop, you should carry the component the machining action is intended for proper fit.  The machinist will then know exactly what he is working with.  Lesson learned I am sure with the aftermarket king pin diameter...maybe for a small tweaking fee the machine shop will adjust the initial job for the correct fit.

[motoMark]

Yeah, I guess I should have taken the uprights (supports) off the car and brought them along with the spindles. Didn't think about that, and yes, lesson learned. I'm going to call the guy who did my machining and see what he recommends. He specializes in antique and classic car restoration, so I'm sure he'll have the right answer.

 

[keithb7]

My ‘38 Chrysler, I can feel a little king pin wear. I’ve never performed this work, yet I suspect I will be in there at some point. I’m seeing the effects on my tire wear pattern. 
 

Front end up on stands, I pump the king pins up with grease and notice the play is gone. Go for a short drive its back to the way it was.  

[Bryan G]

I've felt this disappointment numerous times now, with my current car and some others. You trust the experts who specialize in parts for our baby, only to find stuff like this. I know beggars can't be choosers, but certainly stuff like this is frustrating.

[Sniper]

One needs to realize that new king pin kits are designed to be reamed to fit, they do not fit out of the box and that is not a problem with the supplier.  There is a whole section in the FSM on how to do it.

[Young Ed]

7 minutes ago, Sniper said:

One needs to realize that new king pin kits are designed to be reamed to fit, they do not fit out of the box and that is not a problem with the supplier.  There is a whole section in the FSM on how to do it.

Don't you typically only ream the bushings not the upright?

[Dodgeb4ya]

I have never had to ream outnthe supports or truck axle I- beams when doing king pins.

The MoPar,TRW, Moog USA king pin sets just required the bushings to be sized...NOT the knuckle support or truck  I-beam.

The kits being sold today are sized wrong but will work with additional machine work.

The pins need to be a tight interference fit in the knuckle support as mentioned.

Glad I only use old stock non import goofy sized parts.?

[kencombs]

52 minutes ago, Dodgeb4ya said:

I have never had to ream outnthe supports or truck axle I- beams when doing king pins.

The MoPar,TRW, Moog USA king pin sets just required the bushings to be sized...NOT the knuckle support or truck  I-beam.

The kits being sold today are sized wrong but will work with additional machine work.

The pins need to be a tight interference fit in the knuckle support as mentioned.

Glad I only use old stock non import goofy sized parts.?

My experience also.  The only exception is some older I-beams would egg out the pin hole if ran with loose bushing for too many miles.   There were oversized pin kits available for that.  took a different reamer as the ones used for brass bushings didn't last well working in a steel axle!

 

Maybe the current manufacturers of the kits are using the specs from one of those old OS kits?

[motoMark]

19 hours ago, Dodgeb4ya said:

I have never had to ream outnthe supports or truck axle I- beams when doing king pins.

The MoPar,TRW, Moog USA king pin sets just required the bushings to be sized...NOT the knuckle support or truck  I-beam.

The kits being sold today are sized wrong but will work with additional machine work.

The pins need to be a tight interference fit in the knuckle support as mentioned.

Glad I only use old stock non import goofy sized parts.?

 

Since my new bushings were reamed to fit the new king pins, I figured my best option was to resize the supports. So I'm using my 2-stone brake cylinder hone to increase the hole size to fit the pin. It's a slow go, but I'm making progress. Just about done with the driver's side, still have to take a little more off the bottom to get the pin to slide all the way through. Kind of feel like MacGyver a little bit, but it'll get the job done.

 

[47 dodge 1.5 ton]

If cars are different than trucks, then below does not apply. Trucks have bearings in upper & lower supports , pin close to size in axle spindle.
 

Do you still have a press fit on the OD of the bearing?
  Mine and others that I have done, bearings are pressed in the supports, then ream to fit pin. Alignment to upper and lower support is critical therefore there is a special adjustable reamer that locates on the opposite bore after the bearings are pressed in.

 Unless that hole is egg shaped, should not have to ream the support as mentioned before. You would then need an oversized bearing to obtain press. If no interference, the brg will spin in the support hole.

  

 

Edited March 22, 2023 by 47 dodge 1.5 ton

[47 dodge 1.5 ton]

This is a picture of the type of reamer recommended (larger version), locates by a tapered collet/nut with extension rod to reach the needed locating bore.

Edited March 22, 2023 by 47 dodge 1.5 ton

[motoMark]

The hole in the support that I'm enlarging (as seen in the photo above) does not have a bushing. Only the knuckle contains pressed in bushings that need to be reamed when replaced. The king pin does not rotate in the support, it is pinned, so no need for a bushing.

[47 dodge 1.5 ton]

Sounds like you are on track. I was mistakenly thinking you were opening the bearing bore prior to installing the brg. I did throw some heat to the spindle and drove new king pin in as it was close to size with some press interference. As you stated, taper pinned so may not need any press.

[James_Douglas]

For 0.005, just take a brake cylinder ball home and run it in the upright hole until you get the pin to slide in nice.

 

One thing I will mention is for folks to go read my posts on using torrington needle bearings as apposed to bushings.

 

I think that any of the old cars with manual steering that I can get a needle bearing into the upper I would do it. It just turns better.

 

James

 

[kencombs]

3 hours ago, James_Douglas said:

For 0.005, just take a brake cylinder ball home and run it in the upright hole until you get the pin to slide in nice.

 

O

 

 

Agree, but 'nice' means a tight thumb press fit, not slide easily.   Any motion that could result from too loose will eventually egg shape the hole.

[D35 Torpedo]

11 hours ago, James_Douglas said:

For 0.005, just take a brake cylinder ball home and run it in the upright hole until you get the pin to slide in nice.

 

One thing I will mention is for folks to go read my posts on using torrington needle bearings as apposed to bushings.

 

I think that any of the old cars with manual steering that I can get a needle bearing into the upper I would do it. It just turns better.

 

James

 

How do they hold up long term? Generally, a bushing is better than a bearing for all out strength. There is more surface area in a bushing. 

[James_Douglas]

In response...

 

The tapered pin that wedges in to hold the king pin makes it so that the  king pin does not rock in the hole. When I say a nice fit that drops in I mean JUST slides in without any side movement.

 

Torington needle bearings have the same strength as a bronze bushings AND they are less susceptible to cold flow under heavy loading.

 

The top bushing or bearing is under tremendous side thrust pressure. The bearings are much better than the bushing are resisting the side thrust.

 

James