hydraulic motor for use as gear box

You could do that, but I don't think you would want to. Hydraulic transmission is highly inefficient. Take the current performance, and cut in half, at least, probably more. As far as I recall, the pump on my

If you don't need massive full power full speed reverse, you could rig an electric reverse, as I think the gold wings use.

"Ecnerwal" wrote: (clip) You could do that, but I don't think you would want to. Hydraulic transmission is highly inefficient. Take the current performance, and cut in half, at least, probably more.(clip) ^^^^^^^^^^^^^ I am sure you would not want all the power, both forward and reverse, to go through your hydraulic transmission. Since you probably just want to creep in reverse, I don't see why the hydraulic wouldn't work. I would keep the present power train, and when you want reverse, put it in neutral. Then, taking hydraulic power from a takeoff, you could drive the rear axle slowly in reverse. That would probably give you more than an electric reverse drive could.

as pointed out by others, beware of Reynolds number in hydraulics - sizing for full HP is possible, but if you undersize the piping or have sharp bends, etc, you can loose a whole lot of power. Properly sized it's quite efficient. but it is probably not your best design choice.

consider a small electric motor for reverse? like from a windshield wiper??

Lotus Seven replicas that run motorcycle engines often use a starter motor (automotive I believe) for reverse. Karl

Automotive starter motors usually have a sliding gear on the output which disengages when the current is switched off.

Not from a farm machine and not cheap but may give you an idea.

Martin Riggins