For some while now i have had a vibration issue with my car at speeds above 60 MPH. I tried a few things including replacing all four tires, alignment, balancing. Today I got my tires rotated and then took it on the highway and the vibration was gone? Does anyone know how the vibration can go away just like that? could it of been a bent wheel that was on the front and is now on the back?

 

that is exacly what it is.

just keep the wheel on the back

i accidently bent one of my wheels with the tire machine,
same thing. oops

 

Balance if a big issue on 4runners. They just moved the tire out of balance to the rear where it is more stable. Search for balance you will find why it can be hard to get a good balance. I know you just had them balanced but they may not be perfect.