I replied to the post you made on my profile. I don't have a complete gearbox for a hydrostat but do have parts and some of the parts are the same as gear drive so should be able to help you out.
Have you taken it apart yet to see what the problem is? I don't have any good hst gearboxes right now and yes they are different than the gear. But they do share some internal parts which i would have.
As @North Idaho Wolfman said kubota uses their own hydrostats in tractors. But consider yourself lucky to be able to buy a new hydrostat for only $2k. Most old kubota hydrostat units are much higher than that
As long as its in neutral and brakes off its perfectly fine. Just remember with hydrostat steering you have little to no steering without hydraulic flow
I agree with @North Idaho Wolfman kubota does a great job at diagrams and cab help you more than you would think. Pay attention to details i bet you can figure it out
Tractordata is great don't get me wrong but the information provided is not by kubota. Its a guy who created the site and there are some errors. The 60" is a rck but the 72" is an rc. Both are 27b though