Well shoot, tried to copy it all on here but the diagrams didn't copy. The diagrams can be found along with this narrative here:
Pinion Angle:
http://wolferacecraft.com/pinionangle.aspx
Pinion angle is the difference between the driveshaft angle and the pinion angle on the differential.
See bottom of page for pinion angle recommendations
To measure it you must be able to work under the car with the suspension fully loaded and the car level. You can place jack stands under the rear-end and under the front control arms (as close to the ball joint as possible). A drive on lift will also work for this.
There are two easy ways to measure your pinion, depending on the measuring device you have.
Protractor Measuring Device
Using an angle measuring gauge (adjustable protractor) to measure the difference between the pinion flange and the drive shaft directly. These gauges are available for under $10 from a hardware store.
Place the edge of the gauge vertically against the front of the pinion flange, beside the driveshaft.
Extend the measuring arm forward parallel to the bottom of the driveshaft.
Extend a straight edge under the driveshaft to the measuring arm of the angle gauge.
Hold the straight edge flat against the bottom of the driveshaft and adjust the measuring arm to read the angle.
Depending on the gauge you use, you may have to subtract 90° from your reading to get the correct number.
Your final measurement should be between 0 and 5.
Examine the diagram at the bottom to determine if the pinion angle is nose up or nose down.
Angle Finder Measure Device (Gravity type)
Using a gravity angle gauge (Available at hardware stores) to measure the angle between the driveshaft and the ground & the pinion flange and the ground.
Hold the gauge on the bottom of the driveshaft. Align the gauge front-to-back under the car in line with the driveshaft and read the number from the gauge (Note if angle is up{+} or down{-}). Write down this number.
Next, hold the side of the gauge against the front of the pinion flange (beside the driveshaft). Write down this number (Note if angle is up{+} or down{-}).
Subtract the first number from the second number. This is your pinion angle
Examine the diagram at the bottom to determine if the pinion angle is nose up or nose down.
Pinion Angle Recommendations:
Suspension Recommended Angle
Using Full Wolfe Race Craft Suspension - all solid mounting points. -1 to -1.5
Half Solid & Half Poly Mounting points -1.5- to -2.5
All Poly mounting points -2.5 to -3.5
All Rubber mounting points -3 to -4.5
The more you get away from having all solid mounting points the more the rearend is going to try and rotate upward during launch. Therefore the more angle you must start with to prevent the angle from becoming positive (+). The idea is that when the rearend rotates you want the angle between the driveshaft and the pinion would be 0.
