I added a grapple control to my l3400. I went with electric over hydraulics.
I installed a marine switch on the dash.
I ordered the wrong valve because I ordered an open center valve. We have open center system, you need a tandem center valve
It uses a D03 base, here is the link.
Northman Fluid Power Hydraulic Directional Control Valve 19.8
GPM, 4500 PSI, 3-Position, Double Solenoid, Tandem Center Spool, 12 Volt DC Solenoids, Model# SWH-G03-C6-D12-10 | Power Solenoid | Northern Tool + Equipment
Here is a link to grapple project on a L3400.
http://www.tractorbynet.com/forums/a...ks-bucket.html