Upper vs. Lower Control arms to adjust rear pinion angle?

[Tumbleweed]

I need to adjust my pinion angle in the rear. I still have the stock drive shaft, for a while.
I've read that it is better to use the uppers to control the angle and lowers to locate the axle.
I'd like to know why it is better done that way. It would seem that either would work, unless I'm missing something. Quite likely!!!

Thanks, Jerry.

 

[Rubi Freak]

I just completed all 8 adjustable control arms on my Rubicon. I was told by Clayton Off Road that on the front, the lowers control the wheelbase length and the front uppers are used for the pinion angle. On the rear is opposite. The uppers control the position of the axle (wheelbase length) and the lowers adjust pinion angle.

Anyways, im happy with the way it came out and I was able to push the front axle forward more and the rear axle back a bit. Jeep definitely handles better.



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[wayoflife]

I need to adjust my pinion angle in the rear. I still have the stock drive shaft, for a while. I've read that it is better to use the uppers to control the angle and lowers to locate the axle. I'd like to know why it is better done that way. It would seem that either would work, unless I'm missing something. Quite likely!!!

Thanks, Jerry.

There is nothing "better" about it. Even if you could find rear adjustable lower control arms that could be set short enough to give you the pinion angle that you need, you would effectively change the position of your axle and enough so that it you would have a much shorter wheel base, rubbing issues and coil issues. Don't believe me, give it a try and see what happens. It's just simple geometry.

 

[wayoflife]

I just completed all 8 adjustable control arms on my Rubicon. I was told by Clayton Off Road that on the front, the lowers control the wheelbase length and the front uppers are used for the pinion angle.

Assuming you have adjustable front uppers and lowers, the front lowers will set the position of your axle under your Jeep and the front uppers will dictate your "caster". This should NOT be confused with pinion angle as up front, proper caster needs to take precedence over pinion angle or else you will have a Jeep that handles poorly.

On the rear is opposite. The uppers control the position of the axle (wheelbase length) and the lowers adjust pinion angle.

I really doubt this is what they would have said and if this is how you took it, I should point out that it's completely wrong. Just like up front, your lower control arms primary purpose is to set the position of your axle under your Jeep. The rear uppers are used to set the pinion angle and here, you NEED to have it set in line with your drive shaft assuming you have an aftermarket u-joint style one with a double cardan.

Anyways, im happy with the way it came out and I was able to push the front axle forward more and the rear axle back a bit. Jeep definitely handles better.

On a lifted Jeep, you most likely just repositioned your axles under your Jeep back to where they would have been stock. If you went more than that, you would have issues with your coils and experience rubbing of components.

 

[Rubi Freak]

I appreciate the correction Eddie. On the front, Clayton did mention the caster adjustment with the front uppers. I think I just honed in on pinion angle when i was typing. After i finished the rear, it is definitely centered better under the Jeep. The front does appear to be pushed out slightly more than stock. Is it possible i pushed the front out slightly more without running into steering or rubbing issues? I'm only speaking 1/2 inch or so more. Not a huge gain.


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[wayoflife]

I appreciate the correction Eddie. On the front, Clayton did mention the caster adjustment with the front uppers. I think I just honed in on pinion angle when i was typing. After i finished the rear, it is definitely centered better under the Jeep. The front does appear to be pushed out slightly more than stock. Is it possible i pushed the front out slightly more without running into steering or rubbing issues? I'm only speaking 1/2 inch or so more. Not a huge gain.


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Depends on how much lift you have. 1/2" seems like a lot to me even with 3" of lift. Your main problem will come in the form of your driver side front coil bowing forward enough to sit really close to your sway bar and can cause rubbing. The passenger side coil will bow backward and can catch on your bump stop cup and make a lot of noise. You won't notice this all at once but rather, once the coils start to settle and get softer and really, only when wheeling.