With almost no information given, this is completely guesswork. First I am guessing you are talking about a vertical pump. Then I'm guessing it is either a mixed flow or axial flow pump running at such a slow speed and at 450HP. I'm guessing this is basically a high flow, low head pump; a water mover. Probably one stage.
If my guesses are correct, then you should look at your bearings, in particular the bottom bearing (sometimes called a sand bearing). It is not at all unusual for a pump like this to experience crippling vibration with a small bit of imbalance. Typically (just guessing) you have a large weighted, high diameter impeller/propeller hanging on a shaft; once it starts to get unbalanced, things go awry quickly. If one of the lineshaft bearings gets worn, it will also degrade quickly.
Give us a little more information: Make, model, flow, head, shaft diameter, bearing arrangement, open/closed lineshaft. These details should be available in the pump's file folder, if you can find it.