JD 757 Ztrak kills with hydro control levers under all conditions

I need some help. I've looked at wiring diagrams till my eyes bleed. Borrowed the neighbors mower to cut my grass before I left for vacation. I hate doing that when I've got the biggest mower in the neighborhood (3 acre lots).

Whenever I engage my hydro levers, engine dies. Parking brake on or off, seat switch jumpered or not--even with me in the seat and parking break off.

I've confirmed parking brake switch does what it should. No start unless the brake is set if somebody is not in...

JD 757 Ztrak kills with hydro control levers under all conditions