What would cause this fail?

[xj5280]

Great and long day of wheeling... Didn't do any trail harder than a 5-6 rating. I mean, I was hitting the hard lines but didn't have to bump or throttle out of anything (nor have I ever given it a lot of throttle). I just got to mellow part of a trail and started hearing a thump... I tried to diagnose the problem, axle shaft, ball joints, control arms, etc... and everything looked fine. Decided I should turn around, and 100 yards later my axle folded.

Backed it up, duct taped the control arm and winched the axle back and left the winch on it to hold while I limped off the trail to get towed home....

So what would cause it to fail like this? It just yanked the threads out.
- I buried the thread as deep as I could on the joint.
- my lock nut was tight and lock tited
- my CA were even lengths by .1 of an inch

They were RE CA's, is there a better brand? My uppers are/were currie and they have no sign of failing, except now the pinion ate up the passenger uppers tubing so it's done....

Since I have to buy all four again, I'm thinking Clayton but want to make sure there is no underplaying problem that I haven't thought of that would make this happen again...

 

[SleeperXJ]

I haven't seen a torque value for a jamb nut. I'd guess that if it where over torqued that it could pull threads from either the tube or flex joint (depending on which material is softer. You might want to contact RE about this, I'm sure they would like to do their own investigation.
if you're sticking with short-arm, I've had good luck with JKS control arms.

 

[time2getdirty]

Rokmen control arms are machined in house out of 3/8wall tube so not only are they 3x as thick as those, the threads are not going to ever strip.

 

[proracedriver616]

I've got teraflex lowers and they are super beefy. I try to stay away from RE products, but that's just me.

 

[SleeperXJ]

That's a good point... if the tube material is thinner, over torqueing the jamb nut could have caused the tube to deform enough to compromise thread engagement? Hmmm, anyone know what a good torque value is for that nut?

 

[xj5280]

Rokmen control arms are machined in house out of 3/8wall tube so not only are they 3x as thick as those, the threads are not going to ever strip.

Oh yea... Almost forgot about them... Gotta check em out thanks!

I've got teraflex lowers and they are super beefy. I try to stay away from RE products, but that's just me.

It was to good of a deal to pass up. Plus I didn't think an expo/weekend warrior on 33x10.50 MUDs would do this. Thought it was FAIRLY bomb proof.

That's a good point... if the tube material is thinner, over torqueing the jamb nut could have caused the tube to deform enough to compromise thread engagement? Hmmm, anyone know what a good torque value is for that nut?

I snugged the jamb nut tight and called it good. I would be interested to see what the torque value is.

 

[xj5280]

Not that it really helps out the topic but its more pics!

And the point I almost pooped myself... I couldn't get back down the trail I came up because it would of been way to hard with one LCA. Went down another FOrest road trying to get to civilization. Right at the major intersection of a frontage road I'm Locked in!!!!

 

[Hypoid]

Was the set new, or used?

I have seen threaded assemblies fail because:
1) The threads were worn out.
2) The base material was not properly sized for effective thread engagement.

I could spend a lot of time explaining number two, which boils down to quality control.

For my own curiosity, how far do the threads go up the tube?

 

[xj-grin]

I'll say the torque value I use on my Clayton jam nuts is one grunt away from a hernia. Was your pinion in your UCA before the failure, or is that collateral carnage?

 

[xj5280]

I would say a good 3" of thread
The set was bran spankin' new. Used for probably two years on 31's an a year on the new set up w/33s and a locker.

 

[xj5280]

I'll say the torque value I use on my Clayton jam nuts is one grunt away from a hernia. Was your pinion in your UCA before the failure, or is that collateral carnage?

Collateral. Once the lca let go the axle swung forwards and the pinion hit the CA.
Stopping me in my tracks. Since I was off camber when it happened I had to reverse to safely start patching the axle back. Hence the amount of damage, tho it was only two maybe three feet of moving the Cherokee backwards in 2wd.

 

[xj5280]

Xj-grin
This is what the pinion and UCA looked like hours before.

 

[xj-grin]

I have no clue what caused your failure, man... could have been not enough threads, but you said you had at least a couple inches in there. could have been a jam nut I guess... I know in my application it would take some major mechanical assistance to deform my clayton arms, but those do look fairly thin. Sucks, either way.

 

[xj5280]

Just time to thank my lucky stars I was only going 5 mph instead of 65.. Just time to upgrade and just have a few extra JJ joints in the tool box.

 

[xj-grin]

did it eat the threads on the johnny, or the arm? If the latter, spare joints wouldn't have gotten you anywhere...

 

[Gunter]

for the upper arm, i d weld it up and then grind it back to shape.

 

[Gunter]

as for the gate? no PC but keep a lock and bolt cutters and snip the chain go out and lock it back up behind you. def an emergency

 

[Hypoid]

I'd like to see those parts in person. I'm still leaning toward a quality control issue.

Good job on the recovery! It's difficult to analyze a problem while you are shaking a turd out your britches.

 

[YELLAHEEP]

If the jamb nut got loose and stayed loose for a while.... The threads will just twist and bang around. The more that happens the greater the thread tolerances get as the metal wears away..... Then eventually the threads get too thin to hold and strip.

How often do folks actually check those jamb nuts?

 

[Gunter]

i dont know a lot about lifts, but shouldnt the lowers be fixed and the uppers have adjustment?