Anyone ever seen or heard of a common source for a vibration from rear. I own a shop work on this stuff daily but I’m stumped. My wife’s 2015 cruiser 111k miles has developed a vibration almost like a warped wheel or tire out of balance. I have re balanced many times swapped other wheel tires sets and today I’ve serviced t case checked for shavings or issues, pulled both d shafts and checked u joints and lubed. all the wheels spin freely no noise or tolerance. Truck is leveled in front with dobinson spring and strut and dobinson shocks in rear. Wheel is smooth no shimmy or vibrations in front def in rear. All new brake pads and rotor a all around. Nothing dragging or getting hot. Who’s seen it or dealt with it before?