In order to set the pinion angle on a four link car with adjustment capability for example a drag race four link you lengthen or shorten one or both of the upper four link bars to move down or up. Set the angle finder on the face of the yoke where the u bolts go through.
Specialty Products 1 5 Degrees Peterbilt Pinion Shim 2 Piece
How to adjust pinion angle. If your angle is not correct then you must adjust your upper control arms a bit to dial in your pinion position. Place angle finder on bottom of driveshaft and write down the reading. Pinion angle can be changed on radius rod style suspensions by adjusting their length causing the pinion to rotate up or down. Adjust the pinion down to correct acceleration related vibrations and adjust the angle upward to correct deceleration vibrations. If the angle on your pinion is several degrees less than the drive shaft then you need to lengthen your upper arms a bit to bring your pinion and drive shaft closer into alignment. Rotate the pinion so that the ujoint caps on the yoke are pointing up and down.
Generally plus or minus 1 degree is enough to cure the problem. For instance if the driveshaft is 2 degrees up from level and the pinion gear is 3 degrees nose down then you have 5 degrees of pinion angle. In the case of a leaf springequipped car pinion angle is changed with angled wedges shims that are placed between the leaf spring and the shock absorber mount see photo. If the rearend is nose up and its angle is less than the angle of the driveshaft subtract the rearend angle from the driveshaft angle. Pinion angle can be adjusted by adding tapered shims between the semi elliptic springs and the mounts on the axle housing. Sometimes the face.