Chevy & GMC Vans

If you remove the belt and steer both left and right you should not hear the P/S pump. You won't need to steer lock to lock just put some pressure on the steering wheel. I don't think it's the transmission. A transmission pump will whine continuously.

Thats the whole idea Smilie.
Disengage the pump and if the noise persists its his tranny going south, if the noise disappears then its the p/s pump.
Simple.