Hydro operation observations:
I finally fixed the hydro trunnion linkage per standard procedures published here et al, and observed that even with new springs, caps, and proper slot dimensions, I could move the hydro input arm (goes into the hydro unit) a significant amount (which would obviously vary the tractor speed, the thing I'm trying to fix) by hand, because the pivot-plate that the dash lever actuates was rocking out-of-plane on it's pivot. So I ran a spring from the forward end of the long slot in the pivot plate across the top of the hydro to the opposite (right) frame rail, and Voila! the out-of-plane play was eliminated, as was the play at the hydro input arm!
The difference in driving was phenomenal.
HOWEVER, I noticed a characteristic that as I thought about it, seems inevitable, given the design:
As I was pulling a 400-lb lawn roller up short, steep sections of my lawn, the tractor would slow down considerably, and I would have to move the dash lever to maintain vehicle speed, then back off again as I levelled off. Here's what I think: Normally, like when mowing, the trunnion spring system would be sufficient to hold the hydro input arm in position, maintaining speed. However, under heavy load, like pulling a 400-lb roller uphill, the load would try to reduce tractor speed, thereby moving the hydro input arm appropriately AGAINST the spring system, compressing it, and reducing tractor speed. Additional spring pressure is required (additional dash lever) to counteract the slowing effect of the load. If the spring system were not there and the linkage was fixed, it would act like a geared drive, with no loss of speed, except for inherent losses within the hydro unit.
Is this assessment correct? Just trying to understand my new toy and it's personality.