Hydroboost hum and crazy wheel hop?

[corelokt]

I've had a hum or whine noise for a bit, gets loud with engine speed. Yesterday I braked and the front end went berserk with jumping up and down like each wheel was going up and down at different times. As I had fresh Oxy-Acetalene tanks strapped in the back, and small Acetylene tank up front with me, it was an eye opener. My power steering pump and all my belts are fairly new. Will look again, but the front end has always been tight, and kept greased. Miles are just above 50,000. The noise appeared after a hard stop for a driver who stopped short in front of me.
What is the likely cause of this?

 

[poppop]

If the hydaboost has fluid in it and still whines it probably needs replacing. I just had to replace one on my Chevy Dually for the same reason. The wheel hop is called death wobble and is covered extensively on site. Do a search for death wobble and you will find it. the king pins and bushings are worn out. I just rebuilt a Chevy dually that was a government truck and has the same setup as the cucvs. You could not drive it 20 miles per hour without sever wobble and hop.

 

[corelokt]

The wobble was only when I braked and only once. so far.

 

[poppop]

Just getting started, believe me it will probably get a lot worse.