GMC Repair: Shaking/vibrating from rearend, chevy blazer, drive shaft

Question
Hoping you can help. I have a 1997 Chevy Blazer, 4.3l, 4x4, auto trans. U get a strong vibrating, or shaking from the rearend when driving. It usually does this when I start to go up an incline at speeds of anywhere from 45-60mph. It is very loud and you can feel it. I can let off the gas and it will stop. Drive shaft is tight with no play in it. You can shake the rear passenger side wheel and it nakes a popping noise. Seems to have some play in it as well. Any suggestions on this?

Answer
yes get the rims balanced usually a rim that is bent which will make this kind of noise look to the inside part of rim/ If its been in an accident or hit maybe curb but check that first then have it alignment done that way if they cannot align the wheels it may need something else but check those first  Troy Good luck, hopefully its just a mount and balance issue