I have just finished with skyjacker 4" w/rear leaf kit. Its an 87 full size jimmy. Truck was perfect when I pulled it in my shop. Now with the system installed I have a mean vibration at all speeds and sometimes a grinding noise at higher speeds. The grinding is especially loud if I throw the auto in neutral while rollin at 55 mph. I have had the driveline out and the universals are tight and lubed. What the heck? Any suggestions? I haven't lowered anything because all the tech line guys said is not neccesary for only 4" lift. Any suggestions greatly apprecitated, I can not figure this one out. Should I change the universals anyway?