There are many theories, "experts," highly respected experienced racers, and thoughts regarding pinion angle. Count the stars in the sky and you can bet there are just as many ways documented to measure and set your pinion angle. Here at Install University, we want to give a clear and concise look at how we measure and set the pinion angle.
The goal of setting pinion angle is to have both the angle of the transmission and centerline of the pinion parallel with each other under full load conditions. This is accomplished by measuring the angle of the transmission and adjusting the angle of the pinion correctly.
Measuring your pinion angle
A digital protractor makes the job much easier along with an area clear of obstructions under the yokes. You will also need to be able to rotate the rear tires so you can rotate the pinion yoke so the rear tires must be off the ground but the suspension must be at ride height. It does not matter if your car is exactly level, just that it is safe to get underneath without the threat of rolling, shifting, or falling on you or someone else. Always face the yokes from the same side (driver/passenger) of the car when measuring. We choose to always approach the car from the driver side.
Level the transmission yoke so the solid part of the yoke is level in the cross section. Place the digital protractor on the yoke of the transmission running parallel with the car. Record this measurement. In this case an angle falling from the front of the car to the rear of the car of 2.2 degrees was measured.
Level up the yoke on the pinion gear and place the digital protractor on the yoke running parallel with the car. The angle measurement in this case was 0.3 degrees rising from the rear of the car to the front of the car.
The transmission tail shaft angle is 1.9 degrees lower than the pinion angle (-2.2 + 0.3 = -1.9 degrees). When the car goes under full load and the transmission tail shaft raises up the assumed two degrees, both transmission and pinion angles are equal at zero. This puts the pinion angles in the same angular plane as each other and gives you the best possible scenario for your drive line.
Now that you know how to calculate your pinion angle there is one more variable that should be taken into account. The weight of the driver. Weight must be added to the driver seat equaling the weight of the driver before measuring the pinion angle.
At this point some reading this are yelling at their computer screen. "But the internet says I need a negative three degree pinion angle!" Yes, the interwebs do say silly things like this with everyone always perpetuating the incorrect idea.
The goal of setting pinion angle is to have both the angle of the transmission and centerline of the pinion parallel with each other under full load conditions. This is accomplished by measuring the angle of the transmission and adjusting the angle of the pinion correctly.
A digital protractor makes the job much easier along with an area clear of obstructions under the yokes. You will also need to be able to rotate the rear tires so you can rotate the pinion yoke so the rear tires must be off the ground but the suspension must be at ride height. It does not matter if your car is exactly level, just that it is safe to get underneath without the threat of rolling, shifting, or falling on you or someone else. Always face the yokes from the same side (driver/passenger) of the car when measuring. We choose to always approach the car from the driver side.
When you raise or lift the pinion angle you are are directly rotating the rear lower control arm angle effecting the anti squat of the car. This may or may not lead to better tire grip depending on the car. Realize the angle of the rear lower controls arms are an important factor in traction. You can adjust the angle of the rear lower control arms with the use of relocation brackets. What that angle should be will depend entirely on testing you do at the track while finding out what works and what doesn't for your car.
