I understand. The pinion is located in the rearend.
Keep in mind, you are checking the angle at the back of the transmission and at the front of the rear end.
It helps me to visualize it by drawing a circle and then draw one color line at the angle of the transmission/engine and then draw another color line through the circle at the angle of the pinion in the rear end. The lines should intersect at the center of the circle.
The pinion line will rotate clockwise 1 to 5 degrees under acceleration depending on your rear suspension, traction devices, no traction devices and power input. You can consider the trans centerline fixed.
