flow control valve

I'm just into Day Two of owning this 400. Today, I hooked up a cultivator/packer that has power down wheels. The tractor had a pair of lines to the rear and I made connection OK. I'd used this implement recently and knew that the power up/down worked fine and has a newer cylinder on it. It seemed like I just wasn't getting enough psi to make it move quickly at all. On the right side of the tractor below the tank is "Brand" flow control valve. At medium rpm, I went ahead and moved that valve to the point it started squawking, so backed off. I did find a setting where I had decent response to the wheel up/down cylinder. Questions: Was this an add-on valve? What is it supposed to do? I've just started searching forums, etc.

I do have hydraulic seep (not drips yet) coming from the valve block area. Will look at that soon.

I rebuilt and tightened up the parking brake mechanism - sweet, when it does what it is supposed to!
Had a little trouble starting, until I discovered the choke cable had come loose from the clamp on the carb end. I think I'll have to pull the cover and the shaft to get it freed up and working right. Pretty sure it pulled from the clamp because it was bound up elsewhere.

Any advice appreciated!
Wallypedal

If it is a flow control valve that is separate from the hydraulics it is likely for the power steering, does the steering work good now? Checking the amount of oil in the tank would be first, it could be low, and then did you hook the hoses up so forward on the lever is up. The levers can have a float position if set; on a 400 you have to remove the brake side cover to change from float to double acting. 450 they had holes cut in the top for that unless with the 400 someone changed it.The screen for the hydraulics could also be plugged.Squealing at the pump means it was on high pressure. I really liked our 400-450 tractors so have fun with it, I wish I had one of those instead of the second 560 I have now. A manual will help with the systems on that tractor.