Its in the valve body for auger swing in the valve stack on the right side of the combine. I guess you could run it in manual until you've got time to fool with that valve. Does it help to idle the motor down?
I have the answer you need that seems to have been forgotten by most mechanics part # 71365013 is an o-ring that slows the flow of the hydraulic cylinder in the last foot or so.
We are in the process of doing ours again but it has been 15 years since it was last done and we can't remember how to do it.