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Discussion Starter #1
I have a 90 gt mustang with the wildrides s box kit. Wich is the upper and lower torque boxes. I have adjustable uppers and lower control arms. The control arms are at the stock bolt hole location and stock length. Well my car is giving me a little vibration. I checked pinion angle and comes to .5 degrees. I have stock bushings on the housing and upr control arms wich are helm joint uppers and poly and helm joint lowers. Can anyone tell me what the other bolt holes do?
 

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.5 degree on the pinion flange? Or combined between the pinion flange and the drive shaft?
 

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If i remember right the lower bolt holes lower your cars ride hight and uppers raise it...goin off memory here so dont quote me...lol
 

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The holes on S-Boxes give the option on playing with instant centers/ i/c heights and anyi-squat... To set pinion, put a angle finder on balancer or tail shaft and pinion flange. For example, if balancer reads -3 and pinion flange reads 0,your pinion angle ends up -1.5..
 

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Discussion Starter #8
Ok the tranny measures 3.5 and the pinion flange .5. What go i have here. The driveshaft measures 2.0
 

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The only thing pinion angle does is control bind or "roping" of the drive shaft. Pinion angle is an U joint and shaft alignment issue only.

The holes in the upper box set where the angle where the rear end pulls back on the car, so they have minor effect on front end lift. The upper arms pull back, they do not push. Keep that in mind.

The holes for the lower arms have the major effect on hit rear wheel separation and wheelie. These are the arms that have all the forward push. If you have the front of the arms mounting bolt higher than level from the rear bolt holes the rear end will start to separate and drive the tires in the track on launch. If you have it around level or lower the rear end will try to drive under the car and roll the front way up. It will also, if the arm is lower enough in the front, make the rear tires pull up off the track at launch and go into the wheel well.

When you get it right, the whole car will lift on launch, slightly at the rear and a controllable amount at the front. The upper arms are really just a fine tune, since they only pull back. The uppers also enter the rear end.

An instant center calculator is quite a bit off with the Mustang suspension because of the geometry of the arms and spacing between upper and lower arms on the chassis. It behaves nothing like my real 4 link car did, where upper and lower arms were both straight forward and each side pair tied into one close point on the chassis.
 

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Discussion Starter #13
Ok i think i understang this. My pinion flange is -.5* and my driveshaft is 2*. Does that give me -1.5*? If so , is that good or should i put the rear end at 0*?. Thanks
 

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That's kind why I kinda implied to get rid of the poly on the lowers. You might find yourself steering a lost cause at the worst possible time. When they split the real axle becomes your steers.
 

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Discussion Starter #15
Ok got new readings after adjusting rear end.
Looking from passenger side.
T56 tail shaft -2.5*
Driveshaft 2*+
Pinion flange -2*

Did the math and have -4 degrees. Is this a good setting with mix rubber and poly bushings?
 

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An instant center calculator is quite a bit off with the Mustang suspension because of the geometry of the arms and spacing between upper and lower arms on the chassis. It behaves nothing like my real 4 link car did, where upper and lower arms were both straight forward and each side pair tied into one close point on the chassis.
the short upper arm also makes the IC change as it separates...
 
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