BILL - I had a POS '74 Chevy LUV p/u years ago that in winter you couldn't shift from 1st into any other gear once moving for about a mile or two. I ran the thing out to Dad's place one warm winter day and drained whatever oil was in that little 4-spd and replaced it with Hy-Tran. Shifted fine after that.
The old letter series tractors if well worn did have problems running Hy-Tran, mostly leaks from worn seals & bad gaskets. But gear roll-over was worse when shifting from nuetral into any gear because the Hy-Tran didn't slow the spinning gears down as fast. Dad tried Hy-Tran in his '51 M for a year or two, the M was his loader/chore tractor and waiting 10+ seconds to shift into gear after fepressing the clutch was NOT what you wanted. A switch back to 90W and all was fine. But on the newer IH's like the Super M-TA & 450 Farmall, Ht-Tran was required to properly lube the over-running clutch in the Torque-Amplifier. Back in '54 when the first SM-TA's were sold IH sold an additive, T-A suppliment, or something like that for those tractors, and finally created Hy-Tran with Viscosity Oil to lube the T-A properly, and work in the live hyd. & transmission & final drives.
Not sure about the Eaton hydro, but the Sundstrand 15U used in CC's will tolerate a wide range of different oils. I'd do a search for lube spec's on the Eaton hydro, or maybe other brand tractors that use it and see what they recommend.
I would "THINK" Hy-Tran would work in place of 10W-30 motor oil just fine. But I think the lighter weight Hy-Tran would cause the same problem in a manual trans that has 90W & 140W gear oil recommended as what Dad had in his M, leaking & gear roll-over. I think both WH & Simplicity used Peerless transmissions, they used a LOT of small needle bearings... and IMO, Hy-Tran would do a better job of lubing them than 90 or 140W, but may not be as good a lube as a heavier oil if they were worked/pulled really hard in warm weather.