External hydro cylinder on TO-35

Do I need this?
Part TS300 - SELECTOR/ISOLATOR VALVE

If I want to run an external cylinder and not have to chain the 3 point down...

You don't say if this ram is single or double acting. If it is single-acting (power one way) you do not need any valves to operate it, you simply use the tractor Draft Lever to power it up and down and to hold in any position.
If it is a double-acting ran (power both ways) you will need a spool valve on the tractor, move the lever either way to operate the ram. BUT you must first power the spool valve by lifting the Draft Lever to the top of the Quadrant, the oil is now circulating, so you operate the spool valve to operate the ram. While you are doing either of these things, the Position Control Lever should be on the FAST mark on the Quadrant. You should not leave the Draft Lever at the top of the Quadrant with the single-acting-ram or when you are not using the ram or it has reached the position you want the ram to be. NEVER leave the Safety Valve blowing which will happen if you have the draft lever at the top of the quadrant and the ram is fully extended, when this happens move the draft Lever forward to the Neutral position. To set the Draft control lever to operate the single-acting ram, lift the draft lever and its marker underneath, up the quadrant until the ram operates then move the draft lever forward until the ram neither opens or closes. Now at this point lock the Draft lever marker to the quadrant and then just operate the Draft lever only to lift/lower & hold in the range of the Draft lever marker. You should NOT return the oil from a Spool Valve into the oil filler on the transmission, it returns to a plug on the left side beneath the seat, just in front of the cross-shaft. On a TO35 or any 35 or 65 there is no need to hold down the lower link arms to get external hydraulics. If you need the info about operating this hydraulic system, email me and I will send it to [email protected]