Centering rear with adjustable control arms - Chevelle Tech
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post #1 of 8 (permalink) Old Sep 16th, 19, 2:50 AM Thread Starter
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Centering rear with adjustable control arms

I’m told it’s quite common to not have your differential centered in a factory vehicle. I installed Currie rear arms with adjustable uppers in my 67 Chevelle. I set them to the factory upper length when I installed them. Since I’d like to get as much rear tire width as possible, I found my differential is shifted .5 of an inch to the left. My body is lined up with the frame reference holes.

When I try to even it out, is it better done with springs and shocks in place? Weight on the wheels or unsprung?

In adjusting it, I’m guessing I want to lengthen the arm on the “short side” while shortening the “long side” and equal amount of turns. Correct?

Thanks in advance.

Joe

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post #2 of 8 (permalink) Old Sep 16th, 19, 11:33 AM
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Re: Centering rear with adjustable control arms

This UMI video pretty much explains it.


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post #3 of 8 (permalink) Old Sep 16th, 19, 12:21 PM
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Re: Centering rear with adjustable control arms

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Originally Posted by Kopfjaeger View Post
I’m told it’s quite common to not have your differential centered in a factory vehicle. I installed Currie rear arms with adjustable uppers in my 67 Chevelle. I set them to the factory upper length when I installed them. Since I’d like to get as much rear tire width as possible, I found my differential is shifted .5 of an inch to the left. My body is lined up with the frame reference holes.

When I try to even it out, is it better done with springs and shocks in place? Weight on the wheels or unsprung?

In adjusting it, I’m guessing I want to lengthen the arm on the “short side” while shortening the “long side” and equal amount of turns. Correct?

Thanks in advance.

Joe

I did mine with springs and shocks installed, jack stands on the frame at all 4 corners and floor jack under the diff. I would adjust a bit then let the axle down, jack it back up and measure. I also lined my body up by measuring the frame to wheel lip, not using reference holes. That way you KNOW the body is centered on the frame. Mine was out about the same amount.

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post #4 of 8 (permalink) Old Sep 16th, 19, 12:54 PM
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Re: Centering rear with adjustable control arms

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Originally Posted by OO52 View Post

I have tried that, it does not work. It cocks the rear to the side but also makes it turn at an angle to forward/rear travel. So when you do a burn out and finally gain traction the rear of the car violently jumps over to which ever side has the longest upper link. Depending on how much you have corrected you will have less or more of this.


The rearend needs to be perpendicular to the frame. You would need adjustable lowers and uppers and even then I wonder how much rear "bumpsteer" would be input during rear suspension travel with unequal side to side bars.


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post #5 of 8 (permalink) Old Sep 16th, 19, 1:15 PM
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Re: Centering rear with adjustable control arms

The lowers should keep the rear end square, the uppers set pinion angle and center.
77 cruiser and hydro462 like this.

Tighten it till it strips and back it off a quarter turn.
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post #6 of 8 (permalink) Old Sep 16th, 19, 4:49 PM
 
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Re: Centering rear with adjustable control arms

The lower arms, which weren't included in the above video, control wheelbase and thrust angle.

That video is on the list. We just didn't shoot it yet.

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post #7 of 8 (permalink) Old Sep 16th, 19, 5:07 PM
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Re: Centering rear with adjustable control arms

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Originally Posted by Alwhite00 View Post
The lowers should keep the rear end square, the uppers set pinion angle and center.
This.

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post #8 of 8 (permalink) Old Sep 16th, 19, 5:24 PM Thread Starter
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Re: Centering rear with adjustable control arms

Thanks all for the tips. So two full turns should put me close.

Tom, My measurements were taken from the frame to the axel face, so my differential is not centered in the frame, but you bring up a very valid point. If I’m looking to maximize my tire width, I need to see where the rear is in relation to the body. I just assumed the body would be symmetrical. It may not be, especially since my quarters and wheel wells were replaced.

Joe

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