School me on transmission PTOs

I have a piece of equipment that has an Allison AT545 trans in it. I'd like to move the hydraulic pump to the transmission from the motor because of a long list of reasons I don't have time to type :) However I'm a complete newb on PTOs. I'll be putting a fresh trans in at the same time and the Weller Truck store that I'd be getting it from recommended a Chelsea 230 series PTO. It's air activated because I'll be kicking it in and out a lot. Here's my questions: Does the transmission have to be in neutral to power the PTO, or will it work in drive/reverse also? I ask that because this has hydraulic steering on it and I'll need hydraulic power as its being driven. Some told me yes but it will make horrible noises while being driven. I don't want to tear anything up, I just need a setup that works. Thanks for any and all help here.

Justin

School me on transmission PTOs