JLUR FAD delete kit

[Jtphoto]

The JL axle may have the same relative angles between the pinion and steering. But if the axle sits lower relative to the transfer case output, the shaft will run at a steeper angle, inducing vibration.

And how much lift do you think that takes? I ran 5” lift on 2 different JKs with no vibes, no steering issues, 2.5” and 3.5” on 2 different JLs..

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[jadmt]

no vibes on my 24 jlur with AEV 2.5 that lifts about 3.5. geobrackets and caster ~5°

 

[grimmjeeper]

And how much lift do you think that takes? I ran 5” lift on 2 different JKs with no vibes, no steering issues, 2.5” and 3.5” on 2 different JLs..

I haven't studied the problem enough to know. It is my understanding that there is no hard and fast rule. Just tendencies. Basically, there is no simple answer because "it depends" and it varies between any two specific Jeeps for no apparent reason beyond manufacturing tolerances being so loose.

But this is not new. XJs for more than 25 years have had possible vibration without a SYE in the transfer case starting somewhere around 3" of lift. But some would vibrate at 1.5" while some would be fine at 4.5".

JL front axles have a tendency to vibrate without FAD but it's inconsistent. More lift raises the possibility.

 

[CarbonSteel]

And how much lift do you think that takes? I ran 5” lift on 2 different JKs with no vibes, no steering issues, 2.5” and 3.5” on 2 different JLs..

Out of morbid curiosity, what was the caster angle on the JL with a 3.5" lift?

 

[CarbonSteel]

no vibes on my 24 jlur with AEV 2.5 that lifts about 3.5. geobrackets and caster ~5°

5 is barely over stock and may or may not be enough to stop the wandering that happens on JLs. I ran 6.5 which was about the limit, but it was very stable.

6.7 was better, but in 4H at highway speeds, I could feel the vibration starting to happen and had to stay at 6.5.

 

[grimmjeeper]

As a point of reference, I have had factory axles where the inner Cs were welded on with a difference in caster of about 1.5°. This kind of variance in factory parts is a big contributor to why some people have vibration when others don't.

 

[Jtphoto]

Out of morbid curiosity, what was the caster angle on the JL with a 3.5" lift?

5.2 degrees on the JL with total toe in at 0.1”. Handles just fine on the highway on long trips.

 

[AdamG]

I did the FAD delete wit the Mopar plate and used the Tazer to tell it no FAD. Didn’t have any vibration before the delete so didn’t expect any after, and there wasn’t. Peace of mind when offroading that 4WD is now a fully-manual process.

 

[CarbonSteel]

5.2 degrees on the JL with total toe in at 0.1”. Handles just fine on the highway on long trips.

Yeah...that did not work on mine--6.5 was the sweet spot. They all have variations with some more than others. Awesome FCA QA/QC in the JL series...

 

[jadmt]

5 is barely over stock and may or may not be enough to stop the wandering that happens on JLs. I ran 6.5 which was about the limit, but it was very stable.

6.7 was better, but in 4H at highway speeds, I could feel the vibration starting to happen and had to stay at 6.5.

I get zero wandering i can take my hands off the wheel 70mph and stay in my lane.

 

[CarbonSteel]

I get zero wandering i can take my hands off the wheel 70mph and stay in my lane.

They all have variations...we have seen it time and time again. What works for one does not for another.

 

[Jtphoto]

Guess I’ve been lucky then both JKs and JLs have been the same at 5-5.2 degrees. I found the Toe is more important to address wander.

 

[jadmt]

5.2 degrees on the JL with total toe in at 0.1”. Handles just fine on the highway on long trips.

ditto on mine as well. literally one finger steering at any speed. and my previous 4 JK's all lifted at least 3.5 same and about the same caster and toe

 

[driventoadventure]

Ok probably a dumb question but why the tendency for vibration at freeway speed on a JL but not a lifted F250 for example?

Because most of them have locking hubs which can decouple them from the driveline.

 

[Generoller]

The JL series front axles should have had the mounts rotated more than they are because when lifted, it is a battle between caster versus driveshaft angle. Vibration does not always happen particularly at less than a 3.5" lift, but it can be.

Ford does not have that issue.

The OP never said why he wanted to eliminate the FAD, but I agree with @roaniecowpony, the FAD itself is not the weak link, it is the housing and a FAD delete will not circumvent that.

Well, I was on an offroad adventure where my FAD would not engage. Drive shaft rotated in 4lo but front wheels would not spin. It turned out that it was a setting that was turned off on my Tazer. Once turned back on, all was good. I was advised that the same thing could happen as the FAD is known to be a weak link and often fails. To take that chance out, he suggested that we delete my FAD with the spicer delete kit. I am still trying to research if its a bad idea to do so. I have read that some do the delete but also change to RCV axle but my friend, who is pretty knowledgeable doesnt think we need to do that and we can get away with just the delete kit. Hence why I am on here seeking advie from you all

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