HI , time ago i had some vibration issue and  sorted out was pinion / driveshaft angle . Once i understad and used online calculator i found the right way to adjust . In my case was enough some spacer between trans and crossmember , but i have seen also special spacer to be used on rear axle .  You need to buy one digital angle gauge with magnets .  Measures need to be done with car settled down or car rised with  tyres . then you need to remove driveshft and put the gauge on the slip yoke flat vertical surface ( inside where driveshaft seats )  Take note of result angle . Then do the same on axle , And take note of angle . Last thing is to mount the driveshaft and take last angle , magnets helps . With results use online calculator and see what happen . there is a range to stay in .   ( just one thing )  the rear axle with u bolt loose can rotate a little also if you have a stop in the leaf spring  ( am talking on  the hole and nut to center the leaf )  . Hope to be clear enough , this thing is important to have no vibration coming from rear under. 
this is what i used : https://spicerparts.com/calculators/driveline-operating-angle-calculator

Last edited by Alessandro (8/23/2019 10:47 AM)