front end vibration

Could be. The easiest way to check yourself is to jack up the front end and check for wheel end play. If you can move the wheel up and down by hand you have some serious wear issues, most likely wheel bearing/hub related. If you can't move it up/down by hand put a long prybar under the tire and pry up while holding your hand on the top of the tire. If you feel a "thump" or "pop" then you most likely have bad king pins. Either will cause bad vibrations at the speeds you indicated. Also, while jacked up try moving the wheel side to side a bit and check for play in your tie rod ends, this could also cause bad vibrations.

If the tire wear is spotty, like little circles randomly placed on the tire then it may be wheel bearings, if it is a river or channel, meaning it roughly follows one or more of your tread grooves then it is most likely king pins, but still jack the front end up to be sure before a wheel falls off! You can buy a 20 ton bottle jack at any Harbor Freight Tool store for about $19.99, cheap insurance to make sure you don't lose a wheel going down the road.

 

Both
+ bad aligment
Bad shocks
What you use for balanc the steers?

 

I doubt shocks are the cause of the vibration problem, but having 2 year old shocks don't help either, shocks are inexpensive enough where you changing them every year is preventive maintenance.

I bet that having the 2 year old shocks caused the irregular tire wear, which in turn is causing the vibration.

 

Try using Centramatic Wheel Balancers on steers, and change all shocks.

 

I put new front shocks on when I put new steers on.like bone said,they're cheap enough to replace,and since you're in there already,why not.

 

What kind of steer axle do you have? Simple with springs shocks or Hendrickson steertek with air springs?