Hi-- im NEW TO THIS site iv got a d4 2t series tractor-- ive gota d4 that has the originanl oil pres gauage and it is in the white when i crank it but after i run it for about an hour or two the gauge drops to the lower part of the gauge- temp stays the same- do i need to worry about this

There are a few things that could cause it, worn bearings, worn pump,oil diluted from fuel getting in the oil. You could try changing the oil and install a heavier grade oil in it and see what happens as you are in a pretty hot climate. Sometimes the relief valve can be turned in a little to help with pressure esp. at higher RPMs but at idle it still could be low.Change the filters too if they haven,t been changed for awhile when you install new oil.Let us know how things work out. You could pick up a calibrated gauge and screw in the system to test it to make sure the gauge isn,t correct on the reading esp. if you make some changes as I stated.