I've found the "responsiveness" of the hydro to vary on my various hydro tractors. The 149 is pretty quick to respond, the 1650 is a bit slow. I'm not sure if there is a difference due to relief valves or some other internal function.
Moving the trunnion arm tilts the swashplate in the hydro, changing the amount and direction of fluid from the drive pump to the driven pump.
Have you changed the fluid in the rear end? Is it proper spec'd fluid? If it were very low viscosity, it might react differently than a more viscous hydraulic fluid.
Maybe there is even water in there? Heaven forbid.
Just trying to think about what might be different about this tractor for you...
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