This may be a dumb question, but i am kind of in a pickle. I just finished swapping in my d60 and 14ff along with a shackle flip and switch and other doo dads( about 7.5" lift on 38's). After about 45-50mph i get vibes out of the driveshaft because i have not shimmed the rear axle yet. Im suppose to leave tommorow for school so im not sure what to do. The trip is about 500 miles and i can handle the vibes but i do not know if this is bad for the drivrtrain? any input would be great. I just want to get the truck up there and fix it once i arrive if possible.