since that system does not have a traction manifold with flow/combiner valves I'm not sure if i would cap the lines. I would use a straight connector and hook the pressure and return together so the fluid will pass through. If you have problems getting the system to gain pressure in the drive with the lines connected this way then you can try to cap them but be very careful about how much pressure you apply through the drive control. I would be afraid the pressure would build in the pressure line and cause it to rupture. You can use a cap on the bleedoff return line If there is one. It's a small 3rd line that ports overflow bleed back to the tank, some newer units have this. Yours might not, i see it in the schematic coming off the left and right rear motors but not on the front motors. There should also be a brake line on the L & R rear motors, you can cap that one as well.