I like that

Any update? Looks like it'll be a robust machine!

I haven't worked on it in many months. Last year we were so busy with work that I shelved it waiting on winter. Winter is here now in all it's glory but I have been doing some updating to our house and haven't got back on it again. I did work on one of my Cub Cadet pulling tractors and installed a supercharger on it. It's a single cylinder aftermarket block that I converted to an overhead valve engine by using a section of a 455 Oldsmobile head. I hope to get back on the grader soon. I had some thoughts on more of the hydraulic and may try something different. My hydraulic cylinders and powers steering run off the charge pump on the front hydro like yours. I was going to put a separate pump driven off the shaft on the back of the rear hydro but before I do that I want to try something else. I am going to swap out the hydro on the back rear with another ported pump and try to run the front differential off the other charge pump using the back rear as the reservoir. Not sure it will work but I have access to another ported pump. Work interferes with mt hobbies!

The charge pump is only 600 psi at a couple gpm. Won't be enough to drive an axle.

You'd want 6-10 gpm at 2000 psi. (check the hydraulic HP conversion table) but I think 6 gpm is about 10 hp. (not that you'll need all that at the front axle but you'll need to select the correct capacity hydraulic motor to get the wheel rpms in range with the rear axles.

Sounds like you've got some interesting stuff going on there.

Good info, and looking forward to seeing it in the future OP.