rear end tilt
Rear end tilt during suspension movement will depend on your suspension design, length and location of the locators. whether they be leaf springs. parallel, equal length 4 bar. canted shorter upper bars. nascar 2 bar, with the design you use you can have the pinion angle stay parallel, point up or down during movement. With some suspensions having the pinion down at rest, it will point the pinion up under acceleration as the rear of the car squats thus having the u joints nearer optimum angle DURING Full power, mock it up or work on the drafting table with a ruler and compas drawing arcs.