Thanks for the suggestions. I tried messicks but it's not listed yet. It looks like mine has the transmission and engine from the x1100. What got me started in this quest was noticing an extra oil line on the rear of the transmission on a x1120 at the dealer that my unit doesn't have. I just have a huge aluminum cap that looks Like it would be for a pto shaft. I think this is a "charge pump". I'm not real savoy on the internals of a hydrostatic transmission. This all sparked out of curiosity and wanting to know not just how but why things work. I located a wsm for the x900 and x1120. The x900 has the big cap like my unit has. There was a flow diagram in the manual. My best guess is that this "charge pump" does almost nothing on my unit and on the x1120 adds additional or supplemental flow. Perhaps this is where the extra speed (5mph) comes from on the x1120.
This really has my curiosity growing now. If this is the case, I'm now wondering if I can easily add or swap a few parts and tweak some relief valves to achieve this higher speed? Not unhappy with the performance by any means, but if it's doable, why not.... I realize these are all pretty new but I'm hoping someone can school me on the specifics of how this sucker works.