Hydraulics on rear of JD4520

[RedHawkRidge]

Bought a 4520 in late fall 2013. Came with a set of rear hydraulics, which were not optional. So I bought a rear blade with hydraulic adjustment to take advantage of the tractor's outlets. Now I'm appreciative of having the hydraulic control of the rear blade's angle setup - makes plowing snow much easier.
However, I don't understand why changing the blade angle takes place in a violent, rapid movement that's hard to control. The only way I can "calm down" the manic blade movement is to open the valve (a T-handle that sits in a boxy metal enclosure mounted to the rear of the set). The operator's manual only says this T-valve should be opened when connecting or disconnecting the hydraulic lines to the attachment. When I open it to bring the blade movement to a reasonable/manageable speed, the blade can't hold its setting when it meets resistance (e.g. a snow bank that I want to move).
Obviously I don't understand fully how a hydraulic system works, but I don't think it's unreasonable to expect having control to slow down the hydraulically driven movement of an attachment -- what am I missing?????
Jim

 

[arlen4720]

The electro hydraulic valve you are refering to is a bit drastic because it is two position. If you are controlling a small cylinder and/or have the engine wound up, it makes it all the worse.
The little "T" handle you are refering to, is a valve connected across both work ports to bleed the pressure in the lines to make it easier to connect the quick couplings. If left open, the cylinder will flow freely between both sides of the cylinder. You could put a couple flow control valves LIKE THIS inline. That will slow it down. You could get the 4th and 5th SCV's which are the old fashion lever controls, which you can "feather". I have all 3 valves on my 4720, and like both types. All I use the electro hydraulic one for is my grapple, because it has a button on the joystick, which is very handy.
Do you have a cab or open station?

 

[Dutch445]

in addition to the flow control valve, there are also restrictors
that can be placed inline that will slow that angle cylinder down.
see another thread here:
http://www.tractorbynet.com/forums/hydraulics/154578-hydraulic-restrictor-orifice.html

 

[raheimdal]

You could also add a flow restriction washer into the hydraulic line on the blade. Easiest place is behind one of the quick connect fittings that plug into the tractor. It will limit the amount of oil that flows when the valve on the tractor goes to full open.

Since your cylinder is dual acting, putting it in either line will be fine. It will limit the fluid that flows in, of flows out, and slow down the motion of the hyd cylinder.

 

[RedHawkRidge]

Thanks for the replies. I appreciate the information that tells me that 1) I am not doing anything wrong with my hydraulic line hookups or valving. 2) My dealer is woefully ignorant of basic functions of the equipment he sells. I'll work on using the fixes in your responses.
jim