[thstone]

That is probably not the cause of your squealing and vibration problem. The part that you see deteriorated is the strut bump stop. This part provides a final firm cushion when the shock (strut) is fully compressed - without it, the strut would bang onto the stop. A deteriorated bump stop would typically be noticeable when the shock is fully compressed like going fast over large bumps or cornering extremely hard and encountering bumps and then you'd feel a series of "thud" or "clunks" when the strut piston hits against the bottom stop. Otherwise, during normal driving (around town and on the freeway), the bump stop is just along for the ride.

The condition of the bump stop may be a indicator of the condition of the struts and a completely worn out strut could cause the symptoms that you are experiencing but so could several other components.

I would recommend a full inspection of all of the front suspension components along with the front hubs.