Vibration movement in rear wheel(sorry for the long post)

My 99 S10 2wd was recently in a minor accident but the passenger side wheels hit the curb pretty hard. Had to have the passenger side wheels replaced, along with the spindle and control arm on the pass side front. Everything has been fine since. It goes down the road fairly smooth, there is no pull. I have snow tires on the back and all seasons in the front, all the tires are in good shape. Today, I was going down the highway at 65 or 70, someone pulled up next to me and flagged me down. He told me the pass side rear tire was wobbling back and forth. Not knowing what to do I took it to a nearby Sears auto center(only thing open) They looked it over and said it was fine. The mechanic said the wheel could be out of round but it is more than likely the tire itself. Does this make any since? This is the second mechanic to tell me everything in the rearend is fine since having the accident work done. Do I just drive it and see how it is? Is there anything for me to look for? Like I said it is driving quite smoothly now. Thanks for the help, I apologize for the long post.

Leo
99 S10 2WD 4.3 LS

I would jack up the rear and have someone make the wheel turn, then you can see if it wobbles and be able to tell where. May be a bad tire or rim. It is possible for a bent axle but then it would likely make noise with the drum rubbing the backing plate.

with it jacked up, check for play in every direction. a broken or bent leaf spring could cause this too

Your Post title says "VIBRATION".

Do you feel any vibration, hear any noise, or notice any peculiar swaying or sliding, specifically at high speeds?

When did you last have the tires balanced?

Update--thanks for the responses...I had it in a shop today and they put it in gear while on the lift. The wobble was severe but not too much noise. Turns out it is the axle...they haven't been able to find a used one yet...any idea on how much these go for?

Thanks!