Squaring length-adjustable rear lower control arms.
Imagine looking down on the rear axle in plain view using your Superman X-ray vision. If the axle is cocked sideways relative to the chassis, the car will dog-track down the highway and exhibit different turning characteristics left-to-right.This relationship is adjustable if you have adjustable-length control arms. Simple tape measurements will tell the tale and turning the adjusters will move the axle.
By design, torque arms set the rear pinion angle. This is fine-tuned with the Maximum Motorsports torque arm with shims placed between the front of the differential and the torque-arm mount. The pinion angle is measured using a straightedge and protractor, both at the differential flange and at the transmission. The straightedge is necessary only to transfer the measuring surface away from the crowded torque-arm-driveshaft-differential interface. In the photo, the point where the shims go is just behind the measuring device.