Aluminum knuckle failure

[AnnDee4444]

Dana is welding the inner C's to give 4° of caster at 0° pinion angle, as per Jeeps specifications.

Did you measure this or find any documentation? I've always assumed it was 6°

There's no solve for this?

Not until somebody comes out with a shaft with a CV on each end. Using a single cardan joint (regular U-joint) on each end might get close if you get the pinion closer to parallel with the transfer case. Mixing a single cardan and CV joint on the same shaft will only work if the cardan has no angle (pinion pointing towards transfer case output).

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[gato]

Dana is welding the inner C's to give 4° of caster at 0° pinion angle, as per Jeeps specifications. Since many of us are finding better handling with 6°+ caster, that's putting the pinion at -2°+. Couple that to a lifted Jeeps increased driveshaft angle, and vibration becomes a concern at highway speeds and a locked front axle in 2h.

I opted for the 2-piece RCV axle set to avoid that likely vibration. I have zero inclination to ditch the FAD until I upgrade to a larger set of axles with manual locking hubs.

ˆˆˆ This.

I don't have RCVs yet - trying to see how my factor CV axle shafts perform - by either way I want either FAD or locking hubs. There are too many vibrations stories with no-Fad and U-joint driveshasts.

 

[Headbarcode]

Did you measure this or find any documentation? I've always assumed it was 6°

I do all of my major surgeries at a shop, but in the gravel next to the building. Before height changes, I take a baseline angle measurement beforehand so I have a starting point afterwards. Caster has been my priority in the front, so I never measured the pinion.

I can't provide any official documentation. I'm going off of faded memories of posted pictures by someone explaining front end angles. I can't remember the user name because it's someone that fell inactive a while ago, but was a knowledgeable person. It's certainly possible that I have the wrong number stuck in mind. Maybe the zero pinion angle was the confirmation of +6° caster? Shit! Now I've got to dig out the angle finder and get under there.

 

[AnnDee4444]

I do all of my major surgeries at a shop, but in the gravel next to the building. Before height changes, I take a baseline angle measurement beforehand so I have a starting point afterwards. Caster has been my priority in the front, so I never measured the pinion.

I can't provide any official documentation. I'm going off of faded memories of posted pictures by someone explaining front end angles. I can't remember the user name because it's someone that fell inactive a while ago, but was a knowledgeable person. It's certainly possible that I have the wrong number stuck in mind. Maybe the zero pinion angle was the confirmation of +6° caster? Shit! Now I've got to dig out the angle finder and get under there.

I found this: https://www.jlwranglerforums.com/forum/threads/caster-specification-for-the-jl.17016/#post-488011

It's from a JK, but I can't imagine they would lower the caster on the JL.

 

[Headbarcode]

I found this: https://www.jlwranglerforums.com/forum/threads/caster-specification-for-the-jl.17016/#post-488011

It's from a JK, but I can't imagine they would lower the caster on the JL.

I can't imagine that either. I'll head back a page and fix those numbers. I feel the rest is still sound.

Thanks for the adjust!

 

[jessedacri]

The angles on the JL are much "tighter" than previous versions--but it could be the UD44 improved those angles, but that can depend on the lift height too. I can say that when I had issues with the DS CrMo axles where they seized between themselves inside the FAD and the driveshaft turned all the time, there was a ton of vibration that I'm sure would have caused premature wear. Aside from that, the vibration was not tolerable for long distances. I'm glad I sorted it with RCV axle shafts. I personally like the FAD and wanted to keep it.

My axle broke at the FAD so there was no way I'd have put another axle with that housing on it. Otherwise I would have kept it - mpg did not seem to take a hit losing it though. Still can pull 20mpg highway on 35s & 4.88s with the 3.6/8AT

 

[gato]

My axle broke at the FAD so there was no way I'd have put another axle with that housing on it. Otherwise I would have kept it - mpg did not seem to take a hit losing it though. Still can pull 20mpg highway on 35s & 4.88s with the 3.6/8AT

Can you share more how it broke? Hit a rock or came down from height? Did you have an aftermarket FAD skid?

I like everything about the FAD (poor man's locking hub) except the giant weakening hole in the axle housing - I tried to beef mine up as much as I could.

 

[19 JLUR Bright Whit3]

Can you share more how it broke? Hit a rock or came down from height? Did you have an aftermarket FAD skid?

I like everything about the FAD (poor man's locking hub) except the giant weakening hole in the axle housing - I tried to beef mine up as much as I could.

Yes. I would like to know too.
I cant get new axles unless I sell my motorhome. LOL

 

[CarbonSteel]

My axle broke at the FAD so there was no way I'd have put another axle with that housing on it. Otherwise I would have kept it - mpg did not seem to take a hit losing it though. Still can pull 20mpg highway on 35s & 4.88s with the 3.6/8AT

I planned for that possibility by installing trusses on both my axles. I think the technology is sound, but FCA in its ever "cost cutting" mode could have done a number of things to make it stronger.

 

[Badfish]

WTF, that is just terrible. Its all about earning the badge.

lol ... fake it till ya make it.

 

[jessedacri]

Can you share more how it broke? Hit a rock or came down from height? Did you have an aftermarket FAD skid?

I like everything about the FAD (poor man's locking hub) except the giant weakening hole in the axle housing - I tried to beef mine up as much as I could.

Yes. I would like to know too.
I cant get new axles unless I sell my motorhome. LOL

I hit a raised berm of dirt going about 25-30mph with the passenger side of the rig. Had to swerve off trail to avoid a speeding biker coming over the crest in the opposite direction. Big long straight graded dirt road with some desert shrubbery and uneven terrain to the side - the uneven terrain is what my passenger side went out into. The front passenger wheel took the majority of the force, and the axle was the only thing damaged other than the wheel pushing up enough to pop a couple fender clips. I was running 29lb wheels and 66lb 35 Patagonia MTs and other than a Steersmarts track bar, the rest of the front end components were stock at the time.

The axle bent a few degrees upwards on that side - it didn't totally break but instead the FAD housing cracked at the spot welds and the tube going from the FAD to the C was pushed upward now that it was loose from the FAD housing's spot welds. Result was some funky camber on that side but was drivable (carefully) home. This pic was from below looking up, you can see the cracked paint between the FAD and tube suggesting upward tube movement, and if you look lose on the spot weld in the top right you can see cracks surrounding it. The other spot weld was a bit worse but I can't find the other pics.

I planned for that possibility by installing trusses on both my axles. I think the technology is sound, but FCA in its ever "cost cutting" mode could have done a number of things to make it stronger.

I think you're safe with trusses if they didn't warp the axle housing going on. I was either gonna do that to a new stock axle or go UD44 and eventually decided to go UD44, but I still feel the urge to truss the front and rear - just am afraid of warping the housing due to the weld heat and whatever the cost might be to get the job done right. What was the ballpark cost of your trusses if you don't mind the question?

 

[J0E]

Happened here too. And he’s only on 35’s.

Where do you get those RotopaX 3 gallon mounts?

 

[CarbonSteel]

I think you're safe with trusses if they didn't warp the axle housing going on. I was either gonna do that to a new stock axle or go UD44 and eventually decided to go UD44, but I still feel the urge to truss the front and rear - just am afraid of warping the housing due to the weld heat and whatever the cost might be to get the job done right. What was the ballpark cost of your trusses if you don't mind the question?

It is hard (believe it or not) to warp the housing when using Artec trusses due to the design--if another brand then all bets are off. The hard part is finding someone who knows how to weld on cast steel as it requires pre and post heating to ensure the welds don't crack. The shop that I had do the work in Houston used an inexperienced welder and the welds all cracked requiring them to buy new trusses and remove/reinstall them. The owner did the work the second time and they were fine.

The cost is about $400 (labor only) or so per axle IF the work is being done while re-gearing and the axle is out of the vehicle--it will be more due to the increased labor if you are only doing trusses. I used the economy of scale method and had it done while it was being re-geared/new axles installed, I had the trusses/gussets/LCA skid plates welded on with the axles out of the Jeep. If a shop wants to either do the work with the axles in the vehicle and/or still assembled, then run from them as if they have the plague. To do it right requires full disassembly.

I had this installed:

Front LCA Skids + Front Truss - https://www.artecindustries.com/jlapexfarmor
Front "C" Gussets - https://www.artecindustries.com/jlinnerc

Rear LCA Skids - https://www.artecindustries.com/jlrlcaskids-weld
Rear Truss - https://www.artecindustries.com/jlapexrtruss

 

[jessedacri]

It is hard (believe it or not) to warp the housing when using Artec trusses due to the design--if another brand then all bets are off. The hard part is finding someone who knows how to weld on cast steel as it requires pre and post heating to ensure the welds don't crack. The shop that I had do the work in Houston used an inexperienced welder and the welds all cracked requiring them to buy new trusses and remove/reinstall them. The owner did the work the second time and they were fine.

The cost is about $400 (labor only) or so per axle IF the work is being done while re-gearing and the axle is out of the vehicle--it will be more due to the increased labor if you are only doing trusses. I used the economy of scale method and had it done while it was being re-geared/new axles installed, I had the trusses/gussets/LCA skid plates welded on with the axles out of the Jeep. If a shop wants to either do the work with the axles in the vehicle and/or still assembled, then run from them as if they have the plague. To do it right requires full disassembly.

I had this installed:

Front LCA Skids + Front Truss - https://www.artecindustries.com/jlapexfarmor
Front "C" Gussets - https://www.artecindustries.com/jlinnerc

Rear LCA Skids - https://www.artecindustries.com/jlrlcaskids-weld
Rear Truss - https://www.artecindustries.com/jlapexrtruss

Nice - those prices seem about right for what I was shopping for, but unfortunately I ended up regearing already so it’d be a disassembly to make it happen. Plus artec’s front kit won’t fit the UD44 anyways so I’m probably back to square one for a bit. The rear could use some beefing though and that’s easier to approach sometime in the future.

 

[JustDave]

I think the fact that he was riding around without a wheel & tire played a huge part in the failure.

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