Good question and one that I'm sure every GV installer was pondering... ...IIRC The manual wants the final angles no more than 1.5-2 degrees{nose down} which is way different than the guidelines everyone is using in performance applications...I ended up setting mine up at 2.5 and have'nt had any cruizing or acceleration vibrations.... ....Technically, the addition of the unit is'nt changing the relationship between the trans and rear....But the shorter drivshaft is changing the working range of the universal joints through their range of motion....Also note the new yoke supplied...The one in my kit is a 1350 piece so it's plenty beefy...