SF Nick

Have a PR44 unlimited with a 1310 Adams offroad driveshaft. I decided to take my caster from +4* to -1* to get my bump stops centered & a better pinion angle. Now I'm having driveshaft vibrations at 40mph & 65+ mph. I can't feel any vibrations I'm only hearing a honing sound. Why would this be happing? Is it bad for my drivetrain? My pinion & driveshaft look to be at a better angle now. Thanks for the help