I built one earlier this week but need to finish designing a low profile pump/valve/reservoir combo to fit into a crawler I am building. So far though it is very strong with other pumps and valves I have for my excavators. I will post pics and details as soon as I am done building the pump and such. Below are some of the ways to make a hydro and cable steering setup from youtube.
Hydro static
https://www.youtube.com/watch?v=VbCCDVEKP2k
Cable
https://www.youtube.com/watch?v=QEgDi36XkvA&t=1s