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Discussion Starter · #1 ·
My rear end is not centered !!! If I mount two big tires on 5.5 inch backspace wheels, the left side fits with good clearance and the right tire contacts the exhaust pipe and quad shock. Also the quad shock slightly rubs the main shock on that same side but clears on the left wheel.

I made some careful measurements and it appears the backing plate for the left side is 3/4" or so further out from the frame than the right side backing plate. This is also about the same tire error I see when referenced against the fenders with a long straight edge laid across the tire sidewalls.

So the distance to frame rail says the rear end is offset toward the driver's side. If it was pulled back 3/8th of a inch each side would be equal and nothing would rub.

If I measure the alignment of axle to reference points like the rear bumper or cross member it is not skewed. It appears to have shifted left 3/8 inch without cocking forward or back on either end.

Is this something an fully adjustable upper and lower bar setup will fix?? Is this a frame shop job? Nothing appears to have been hit. The floor pans show no sign of buckling.

If this was a normal ladder bar or linked rear end, I'd crank the pan-hard adjustment. How do I fix this? Anyone ever have this happen?

Tom
 

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alot of fox body owners complain about a wheel sticking out further on one side. if you search the threads i think there is quite a few on here. i dont know how to fix it or what causes it, i just know its common on these cars.
 

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Because of the stock rear suspension setup's geometry and the huge amount of slop in the rubber bushings, the rear end is free to go just about anywhere it wants at any angle it wants. A good set of adjustable upper control arms would probably be a good step towards fixing the problem.
 

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My axle is the same way. Its due mostly to Ford's liberal tolerance of aligning the body to the subframes. I bet if you measure the axle to the control arm pickup points it would be perfectly square. When I installed my MM torque arm and panhard bar the instructions said not to be surprised if I found this problem. It also said that up to 1/2" difference is normal and it was better to have the axle centered to the control arm pickup points than to force the axle out of alignment to center it with the body.
 

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My rear end is not centered !!! If I mount two big tires on 5.5 inch backspace wheels, the left side fits with good clearance and the right tire contacts the exhaust pipe and quad shock. Also the quad shock slightly rubs the main shock on that same side but clears on the left wheel.

I made some careful measurements and it appears the backing plate for the left side is 3/4" or so further out from the frame than the right side backing plate. This is also about the same tire error I see when referenced against the fenders with a long straight edge laid across the tire sidewalls.

So the distance to frame rail says the rear end is offset toward the driver's side. If it was pulled back 3/8th of a inch each side would be equal and nothing would rub.

If I measure the alignment of axle to reference points like the rear bumper or cross member it is not skewed. It appears to have shifted left 3/8 inch without cocking forward or back on either end.

Is this something an fully adjustable upper and lower bar setup will fix?? Is this a frame shop job? Nothing appears to have been hit. The floor pans show no sign of buckling.

If this was a normal ladder bar or linked rear end, I'd crank the pan-hard adjustment. How do I fix this? Anyone ever have this happen?

Tom
You center the axle side to side with double adj uppers, left to right with double adj, lowers But you may need to adjust both uppers and lowers, it you have to adjust the lowers too much. As this will change the pinion angle. If you adjust right, the pinion angle wont change, as you will be adding just as much as you take away. You will also need to keep your measurements you started with, just to go back to a starting point should you fudge something up. Good Luck
 

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Discussion Starter · #6 ·
Edited this.

Whoops, double posted at same time as you Mr. 89 coupe. :bigthumbsup Thanks for help. I understand what you are saying after looking under the car....

I just posted this below while you were posting that. :D...

Thanks for the help. I spent some time under the car earlier today.

The upper control arms length ratios determine the centering. One of the upper control arm brackets was never perfectly aligned. The poorly fitting battle boxes I installed did not help because they located off the original holes. Some original spot welds also have pulled loose.

I'm going to pull things as far as I can over and then wire weld all along the brackets.

When I receive the fully adjustable upper and lower arms it will be a simple matter to offset the rear end side-to-side by adjusting the upper bars length ratios, and keep the rear end straight by adjusting the lower arms length and the pinion angle by mean length of the two upper arms and the lower arms.

I only need to bump it over 3/8th inch to be perfectly centered and solve all the problems.

Tom
 

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Yeap, if your control arm mounting points are off, this will do this also. I had forgot that you installed the battle boxes, as that would have been my first guess had I remembered. Ford was not to meticulous on there mounting points. They just did enough for it not to be a problem, considering the equipment they used. As you start to make adjustments in tire size and suspension, these things become magnified.
 
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