when i hit a series of bumps, my rear end starts to move to a side like there is no contact between the road and vehicle. the shocks are stock and there is about 60k miles on my 99 4Runner Limited. If not shocks then what else could it be?

 

Sounds like a symptom of worn shocks to me. With 60k miles on the stock shocks it does seem reasonable to assume that they are worn and may need replacing. Does it look like they're leaking?

 

no leaking from what ive seen. just couldnt figure out if it is shocks or just cause the rear end is light.

 

My '96 does the same thing over washboard on the Forest service roads. I have Monroe Reflex on the back end, and it doesn't make much difference. It's the nature of the beast: solid axle and coils. Try airing down your tires or slowing down. That's the only things I've found that helped.

 

Jump off your rear bumper....if it rebounds and returns to rest right after, likely the shocks are fine.
The 4runner does have a light rear end so it can feel like it skips around when going over bumps.