Steering problem diagnosis?

[Blue68]

Here's one for you steering gurus. My power steering is posessed. When I turn the wheel real hard and quick to the left, it will keep right on turning until it hits the stop. Of course, I'm doing this with it sitting still. Is it the steering box or the pump. Seems to me it should be in the box, right?

Help please.

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'68 C-10 LWB, '98 Z-71 350 w/accessories (Serpentine), Edelbrock Performer, Edelbrock 1405 (600cfm) carb, GM HEI, CompCam Extreme 4x4 roller cam, Thorley Headers, Carter Electric Fuel Pump, Vintage Air, 700r4, 3.73, disc brakes and power steering upgrades.


Way too much money and time..But it's a hobby.