Swap hydrostatic trans between 16HP and 19.5HP twin

[larry_c]

The engine died in my old 16HP tractor with a 26HP Kohler engine. I got a used LT1000 that has a 19.5 twin (the vintage inline twin cylinder) and it's pretty good, except it crawls uphills. Feels like the hydrostatic is worn.
Can I swap it with my old 16HP (the tranny). It's a different part number on the old one from the new. Is there anything to look at in the "new" one to improve the speed - brakes look ok on it.

Thanks
Larry