It has been a while since I had a 7200 but it seems like there is a section in the operators manual that addresses that issue. I am assuming you are talking about running a vac blower motor. If it is a finger pickup you should not have to do anything.

If the operators manual has a better idea than what I am going to tell you, by all means go with the operators manual.

Here is a flow control valve that will keep your oil from heating. It lets you adjust the oil to send the proper amount of oil to the vac motors under pressure and returning the excess back to the tractor via the return line or better an additional zero or low pressure line to the tractor sump (see tractor manual for an attachment coupler to do this). You would use this in place of the needle flow control adjusting valve that is on the planter now. The needle flow valve on there now just restricts the flow to the amount the blower needs. With a closed center system this is fine as the tractor pump adjusts itself to produce only the flow (gpm) needed to do the job. In an open center system the pump puts out a constant flow instead of a variable rate flow. The planter blower would be ok because the needle flow control valve would still limit the flow to the motor but since the pump on the 6603 would be trying to push full flow (maybe 16 gpm or so?) through the system that only needed about 4 or 5 it could not do it and would cause the relief valve in the tractor system to blow off the excess flow. The planter wold work fine but the tractor would be bypassing so much high pressure oil it would overheat and prematurely wear out your pump and relief valve (a bad thing). Not to mention using a lot of extra fuel when that hydraulic pump was drawing a constant 15 or 20 horsepower to drive the overworked pump. This adjustable flow control valve lets you adjust the lever to give the right amount of oil to the blower (you would adjust the vacume with this lever) and bypasses the rest at low pressure back to the return. Like I said, this valve would replace the original needle valve and you would have an additional return line to plumb into a low pressure return to the tractor sump or valve body.

If you wanted to be able to go back to the 4440 you could either set the new flow control valve wide open and use the tractor flow control to adjust the vac level or set the flow on the 4440 open enough to ensure adequate oil flow and still use the new flow control valve.

Fairly simple and inexpensive fix to be able to use both tractors.

You might have to play with which outlet to use on the 6603. One probably has priority and you need to choose the one where the planter will raise without cutting the blower motor completely out when raising the markers or planter.

A good JD mechanic could probably give more insight to the tractor and planter workings but good mechanics that actually UNDERSTAND how these systems work are hard to come by. Some can turn wrenches and replace parts but a precious few actually understand what is happening within.

John