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Old 08-30-2009, 03:19 PM   #1 (permalink)
Sam
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404 Steering Knuckle coming apart

I have a couple questions. I have a custom 404 / Toyota axle in my crawler and I am having a problem where the steering knuckle joints are backing out. So essentially the axle shaft pushes heavily on the axle tube seal causing it to leak and my CV joint starts to rub on the inside of the knuckle.

1) How can I prevent this from happening? Is there something wrong with my ball joints that I should replace them? The passenger side doesn't have this problem, so I am wondering if it is a wear item or just a common maintenance things.

2) What tool(s) should I use to push it back together. In this picture below it is backed out by about a 1/4 of an inch.

Thanks for the help.
-Sam

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Old 09-03-2009, 05:50 PM   #2 (permalink)
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Actually this is quite common. What is happening is that your king pin bushings are loose. It looks like the problem is with the top, but actually it is the bottom that is loose.
These bushings are pressed in and work loose. I tig mine in place anymore. Easy to do after you pull the entire axle out, bust loose the bottom nut, and separate the top and bottom knuckles.
10 minutes of welding, 6+ hours of wrenching. sorry....
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Old 09-12-2009, 11:30 PM   #3 (permalink)
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Andy do you have any how to/info on your process or is it the same as JR and many others have posted about welding the tops directly to the "inner c's" and grinding them smooth?
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Old 09-13-2009, 09:06 AM   #4 (permalink)
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after I have the knuckle apart, I place it in a press and reseat the hardened steel "pin". since it is hardened, I have it tig welded (I can't tig) just on the top so that it cannot pull back out. I read somewhere that SOME 404's have these bushings with a groove that a pin slides in to keep them from coming loose, but I have not had one of these go thru my shop yet, so I cannot confirm this.
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Old 10-06-2009, 08:34 AM   #5 (permalink)
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do you have a pic of your rig...it sounds interesting.
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Old 10-06-2009, 08:51 AM   #6 (permalink)
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Thanks for the reply weps. Very helpful. When I actually get a chance to pull it apart, I will try and take pictures to document it. I don't have a plethora of tools, so it will be interesting to see if I can do it with what I have I am sure I can tack on a few hours to that 6 hours you quoted.

Thanks again,
-Sam
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Old 12-25-2009, 06:31 PM   #7 (permalink)
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BTT did you ever end up fixing this?
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Old 12-27-2009, 03:28 PM   #8 (permalink)
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I have this happen often since I compete with water in the front tires - extra weight to pull down! I have mig welded it to some benefit but it usually ends up cracking the hardened bushing. I now just replace the knuckles every year with new ones and I have not had any problems on comps. I notice it slipping down but it usually stays together for a while (at least a season).

How do the tig welded ones do? Do they end up cracking eventually?
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Old 01-06-2010, 12:12 PM   #9 (permalink)
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I have this happen often since I compete with water in the front tires - extra weight to pull down! I have mig welded it to some benefit but it usually ends up cracking the hardened bushing. I now just replace the knuckles every year with new ones and I have not had any problems on comps. I notice it slipping down but it usually stays together for a while (at least a season).

How do the tig welded ones do? Do they end up cracking eventually?
jesus new knuckles every year? What does that run u?
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Old 01-17-2010, 10:37 PM   #10 (permalink)
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I can't remember... but I get them from Expedition. I'll know soon as the season is getting close!
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Old 01-27-2010, 12:01 AM   #11 (permalink)
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Here's a little info I've gathered after running mog/9s for the past 9 years.

IMO, the king pin area is the weakest part in the portal section. I've broken more king pins then I can remember and here is what I've learned.

Bashing the wheel rims into rocks breaks the king pins, so stop it!

The next problem is that the lower king pins get pulled out I believe from the shocks topping out which causes a slide hammer effect on the king pins, eventually knocking them out. (hopefully, this has been fixed by adding limit straps to soften the top out.)

Once the lower pins get knocked partially out, there is less contact area and more leverage on the area which then causes the knuckle holes that locate the king pins to wallow out. Once this happens, the integrity is gone and it's a losing battle of re-welding the king pins in place.

The key, I think, is to weld the king pins in place when the knuckles are new while the holes are in good shape.

I've had the upper king pins pull through the roll pins and have welding them in place, also. This turned out to be a bad decision as the upper king pins broke at the groove that is cut for the roll pins. IMO, it's better not to weld the upper king pins and let them float if they must as long as the roll pins stay in tact. Again, I think the upper king pins become loose in their bores when the lower king pins pull out and put more stress on the upper's.

To keep the lower king pins from pulling out, I tig weld them in place with several passes and also weld part of the slotted screw in place. I don't weld the entire screw head as I like to see a little screw head showing so that I can monitor it's location.

Since it's only a surface weld, the weld needs to be built up enough to give it strength. Little dainty tig welds tend to crack at the weld. Yes, the king pins are of a harder material (which doesn't weld good) so that's why the screws need to be welded in also.

NOS Knuckle assembles are $385 each from Epidition and are in a limited quantity. Once they run out, there gone!

My plan is to take the old, worn out knuckles and see if I can't make a bigger king pin arrangement and fastening system.

Here are some various pics of broken king pins and the welded fix.
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Last edited by JR; 01-31-2010 at 10:26 AM.
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Old 01-28-2010, 08:00 AM   #12 (permalink)
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JR,

Would it make sense to try machining out the factory hole slightly oversized, and tap it for a threaded version of that kingpin?? Maybe even make the threaded part of the kingpin extra long so that the protruding part could be drilled for a cotterpin/castle nut retainer??

It's scary to think that replacement knuckles will soon be gone. I guess at that point the aftermarket will have no choice but to come up with a retro-fit / repair for this issue.


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Old 01-28-2010, 07:15 PM   #13 (permalink)
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Hey WEPS, whats the frigin hold up here? Engineer it and start sellin em!

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JR,

Would it make sense to try machining out the factory hole slightly oversized, and tap it for a threaded version of that kingpin?? Maybe even make the threaded part of the kingpin extra long so that the protruding part could be drilled for a cotterpin/castle nut retainer??

It's scary to think that replacement knuckles will soon be gone. I guess at that point the aftermarket will have no choice but to come up with a retro-fit / repair for this issue.


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Old 01-28-2010, 10:16 PM   #14 (permalink)
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There is not much room between the king pin and the c/v joint, maybe 1/4". Certainly not enough room to throw a castle nut on top.
Those German Mercedes people are pretty smart. I don't think there is any easy fast way to make it stronger. The way they have it, it all falls into place and makes perfect sense unless it's getting abused.

If you look inside, you will notice that the casting is pretty minimal.

I think the next step would be to bore the hole slightly and make a solid pin from something like a 4140 hardened material. At the bottom of the pin would be a thrust platform and male threaded protrusion to attach the outer knuckle. The problem is attaching it to the inner knuckle. Since there is no room for a nut, the only thing I can think of to press fir it and weld it. A cerclip wouldn't be tight enough.

I've never had a 406 knuckle apart but I bet it's a beefier set-up.
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Old 01-29-2010, 05:54 AM   #15 (permalink)
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What about getting a hardened washer for right here. A washer that is a larger diameter than the kingpin mabey 1/8 thick. Machine a taper in the washer hole to make the bolt fit flush. Then machine the same thickness off the kingpin..
Either grind the knickle flat or machine it flat so the washer and bolt pulls it all together when you tighten it together?



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Old 01-29-2010, 07:18 AM   #16 (permalink)
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I think it is a matter of getting what you pay for. If you step up to the plate and buy a set of 406-416 axles you guys would not have these problems. The 404 axles are great for what they were designed for, but not what you guys are doing to them. But the stronger 406-416 axles can take all the abuse you can give them. It would make since to just spend the money once and just get them to start with. This way you don't have to buy new parts and rebuild them every year or spend all that extra $$ to reinvent the portal boxes to withstand all the abuse. Spend the extra now and save some $$ later!
But what do I know, I just drive Unimogs, and not buggies. Just my 2 cents worth!
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Old 01-29-2010, 06:47 PM   #17 (permalink)
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I think it is a matter of getting what you pay for. If you step up to the plate and buy a set of 406-416 axles you guys would not have these problems. The 404 axles are great for what they were designed for, but not what you guys are doing to them. But the stronger 406-416 axles can take all the abuse you can give them. It would make since to just spend the money once and just get them to start with. This way you don't have to buy new parts and rebuild them every year or spend all that extra $$ to reinvent the portal boxes to withstand all the abuse. Spend the extra now and save some $$ later!
But what do I know, I just drive Unimogs, and not buggies. Just my 2 cents worth!
While I do respect this sentiment. I don't think 406 axles are gonna bolt up to my 404. And besides, re-engineering this stuff is half the fun. If whatever it is was supposed to do what we are asking it to do, it wouldn't be impressive now would it?

Yes, the 406/416 axles are beefy... but I have broken bigger, more impressive running gear (mostly by being stupid with it). There is no force in the universe as strong as stupid. Besides, I bet a broken 406/416 knuckle would cost even more.

I have been looking at the knuckle problem for a while now; As I would like to have four wheel steering and I am on a budget. Thus far I think the cheapest route would be to get a complete front axle, rape it for parts and then sell off the diff and housing. This also has the added benefit of surplus portal boxes though it does not solve the impending scarcity issue. Besides, hand built custom knuckles would be F***ing cool. With the added plus of being able to use a MUCHlargerbearing. Maybe a bearing out of say an all terrain fork lift trunnion or... well you get the idea.

If only I could get bearing assemblies made out of case hardened stupid.... Hmm...
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Old 01-30-2010, 12:05 AM   #18 (permalink)
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What about getting a hardened washer for right here. A washer that is a larger diameter than the kingpin mabey 1/8 thick. Machine a taper in the washer hole to make the bolt fit flush. Then machine the same thickness off the kingpin..
Either grind the knickle flat or machine it flat so the washer and bolt pulls it all together when you tighten it together?
That might help to hold the king pin in. This solution still requires a hollow king pin though.

The King pin size just needs to be beefier.

406 stuff has a pretty good weight penalty.

Maybe build a set of knuckles from chromo plate like Spidertrax.
Ugh...
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Old 01-30-2010, 09:40 AM   #19 (permalink)
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Has anyone ever broke a bottom kingpin? If it is just the top one wonder about just making a solid top pin, or bore the top hole out for a larger pin..

There was a guy on here that sold a set that he listed as having larger upper kingpins..He said he had his local machine shop made larger upper kingpins...
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Old 01-30-2010, 01:53 PM   #20 (permalink)
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It seems like boring the knuckle for a larger pin might be the simplest thing. The only thing is... doing that will weaken the knuckle. It occurs to wrap the end of the knuckle with a piece of flat stock might be a remedy for this; I have seen this done on Rockwell 5 Ton axles. It may be that if this is done the added support around the pin opening may keep everything from drifting in the first place. I know the guy I was talking to who told me about this had done it and stopped going through knuckles and pins.

One other side thought...

I understand it is common engineering practice to use a smaller bearing in the top of a steering knuckle. I believe the theory is that this joint is generally under less stress that the lower. I don't really understand this however, I think this is done because the joints stack in such a way as to make the lower joint the fulcrum and the upper is only taking a percentage of the lateral load applied tire. So it doesn't need to be as large for normal day to day use. In the OE application for this axle most of the steering stress is taken by the lower pin as well. A high steer conversion on these axles will drastically change the stress applied to the upper pin. This may be the source of a lot of knuckle problems. I am not saying high steers are bad (especially since I am planning one) I am just trying to identify the problem so we can solve it.

Just food for thought.
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Old 01-30-2010, 05:01 PM   #21 (permalink)
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Im interested in figuring something out also. Im in the middle of a disc brake conversion and since Im neck deep in it I figured I'd pull the knuckles and get rid of that camber. While I was looking at the knuckles, after following this thread, I noticed my driver side upper kingpin looks like its worked its way loose. Anyway, seems to me solid kingpins and welding them would be the easiest way to go. Im going to look into options once I get mine apart and realy see how everything goes together...until then, I'll keep following along listening to ideas.
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Old 01-31-2010, 10:34 AM   #22 (permalink)
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Has anyone ever broke a bottom kingpin?


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I've broken more king pins than I can remember
Mostly, bottom ones. It was only recently that I started breaking top pins and I think that is because they were welded.

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Old 01-31-2010, 10:52 AM   #23 (permalink)
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In the OE application for this axle most of the steering stress is taken by the lower pin as well. A high steer conversion on these axles will drastically change the stress applied to the upper pin. This may be the source of a lot of knuckle problems. I am not saying high steers are bad (especially since I am planning one) I am just trying to identify the problem so we can solve it.

Just food for thought.
Very interesting observation.
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Old 02-02-2010, 08:10 PM   #24 (permalink)
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Wow, thanks for all the responses and experienced input. I haven't been able to attack the problem just yet, but plan on tearing into it tomorrow. I have a temporary fix which is a spare set of axles sitting in the garage. Just going to rob from them to make the KOH trip.

I am so unfamiliar with what holds them all together so it is going to be an experience. I will see if I can see anything for improvement, but just from the outer view, it doesn't look like much can be done considering the working space. Honestly it really looks like a newly designed left and right C is the best ticket. Doubt that is happening any time soon though.

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Old 02-03-2010, 11:52 PM   #25 (permalink)
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So I took mine apart tonight. Wow, definitely some interesting fabrication on this one.

My lower king pin was backing out as expected, but I didn't expect the hacked up axle-C. The inner C was ground down on the top and the metal smeared over. There was some home made bolt holding the bearing on because of the ground down C. It looks like a hex bolt was spun up and tapered and a slot put on top. The taper was much smaller than the stock bolt so I think this is what stretched and started to let mine go. Everything seems tight still though, so I will just put some new bushing in if I can find some quickly in the Bay Area. Gotta start looking. I also will replace the inner C and the the bolt of course.

If you have a good suggestion for the Bay Area, please let me know. I would like to put it back together for KOH next week. If I have to, I will pull my spare axle apart and take those parts.

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