U-joints?

BillArnett

New member
The other day I was climbing a not very difficult serpentine trail up a hill. The switch backs required almost full steering lock. And being up hill I had to use a significant amount of throttle. I made it up with no difficulty but I noticed that in the middle of the turns the power seemed to be kind of jerky as if something was intermittently binding up.

I never noticed anything like that on my 2-door JKR.

I'm guessing that the jerkiness is due to the U-joints. Unlike CV joints, U-joints don't turn the two shafts at the same rate over the complete revolution. If this diagnosis is correct then I'm further guessing that applying a lot of power at large steering angles is not a good idea.

I have Cooper STT Pro 37x13.5 on ProComp wheels with 4.75" backspacing. Thus my scrub radius is somewhat more than stock. That may be exacerbating the issue, too.

Comments?
 

JTCO

Meme King
4wd with u joints will be more jerky but not sure if that was what you were experiencing. My wj previously had CV joints in the front and was smooth as butter but now after an axle swap, it has ujoints and I definitely feel the difference. Maybe....
 

NFRs2000NYC

Member
Agree, sounds like crow hopping. Last time I was in moab, I left a trail and drove to town in 4WDhi, but forgot, and had to bust a u turn because I missed my carwash....that wasn't a pleasant experience lol
 

BillArnett

New member
What you're referring to is crow hopping and that might of been what you were feeling.

If "crow hopping" is the effect you get when in 4wd on a hard surface caused by the two axles being forced to run at same rate when they're taking different paths then I don't think that's not what I was feeling. This was a very loose surface, dirt and loose pebbles. "Crow hopping" is kind of irregular and aperiodic. This was very regular and consistently at about 1 hertz.
 

YAHAHA

New member
I get the same thing in my Jeep and F150 when in 4WD and I turn too sharp. I just figured it was the u-joints binding. Regardless of what it is, I don't turn as sharp & it goes away.


It's not just a Jeep, it's an amusement park on wheels.
 

Tellico

Member
The other day I was climbing a not very difficult serpentine trail up a hill. The switch backs required almost full steering lock. And being up hill I had to use a significant amount of throttle. I made it up with no difficulty but I noticed that in the middle of the turns the power seemed to be kind of jerky as if something was intermittently binding up.

I never noticed anything like that on my 2-door JKR.

I'm guessing that the jerkiness is due to the U-joints. Unlike CV joints, U-joints don't turn the two shafts at the same rate over the complete revolution. If this diagnosis is correct then I'm further guessing that applying a lot of power at large steering angles is not a good idea.

I have Cooper STT Pro 37x13.5 on ProComp wheels with 4.75" backspacing. Thus my scrub radius is somewhat more than stock. That may be exacerbating the issue, too.

Comments?

Which CV joints are we referring to, the axle shaft U-joints? Forgive me (I skipped the JK generation) but I thought the JK Rubicon D44s used u-joints as well, so what is the difference between your JK and JL axle joints? The only CV axle joints that I am aware of are on the new full-time JL 4x4 system.
It sounds like crow hop to me. At full lock of the suspension, the inside tire will want to rotate slower than the outside tire and you could get some jerkiness even on loose terrain. I wouldn't think too much of it as long as all the components look good.

As far as gunning it at full lock, that is when I've seen the highest rate of failure for axle-shaft U-joints: steering at full-lock and a lot of skinny pedal. I wouldn't make too much of a habit of it unless the trail required it. It may take some trial and error to see what the new axles can take.
 

BillArnett

New member
Which CV joints are we referring to, the axle shaft U-joints? Forgive me (I skipped the JK generation) but I thought the JK Rubicon D44s used u-joints as well, so what is the difference between your JK and JL axle joints? The only CV axle joints that I am aware of are on the new full-time JL 4x4 system.
It sounds like crow hop to me. At full lock of the suspension, the inside tire will want to rotate slower than the outside tire and you could get some jerkiness even on loose terrain. I wouldn't think too much of it as long as all the components look good.

As far as gunning it at full lock, that is when I've seen the highest rate of failure for axle-shaft U-joints: steering at full-lock and a lot of skinny pedal. I wouldn't make too much of a habit of it unless the trail required it. It may take some trial and error to see what the new axles can take.

Thanks. But that kind of experiment is not one I want to try. The cost of "error" is just too high. Time to exercise an extra bit of mechanical sympathy .
 

Tellico

Member
Thanks. But that kind of experiment is not one I want to try. The cost of "error" is just too high. Time to exercise an extra bit of mechanical sympathy .

I wasnt referring to you specifically, but JL owners as a whole. I think it’s safe to assume that not many people are pushing these new axles to their limits quite yet. I haven’t heard of any busted JL axle shaft U-joints yet, but they are certain to come.
I will be joining you in planning to keep mine intact for as long as possible 👍
 

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