Its simple. Shim the trans to get its centerline level at 0 degrees and then shim the rear to the downward degrees you want to run from 2 to 7 down. I always like to get the trans level at 0 first if I can and then once the rear (pinion) centerline is level you know to nose it down to the degrees you want. Myself I feel its easier for most to work with it if the trans centerline is 0. Ron