Jay P

Running across a weird issue I can't wrap my head around. I have RWD '04 XLT, and when applying gas from a stop position, more times than not it seems the rear generates a quick vibration, almost as if the rear wheel(s) spin, just for a couple seconds. I cannot tell if it is tire, drivetrain/tranny or what. I feel it happens on the passenger side, not both sides, but I could be wrong. Some times is vibrates enough to shake the cabin for those couple of seconds. I'm hoping its as easy as tires... Anyone heard of this?