Oil warning no pressure

[Paul 1957]

Hi guys I'm a new member I have a 2003 for explorer 4.6 290000 miles just lost oil pressure when the car is hot. When you start the car perfect oil pressure runs quiet smooth doesn't burn oil oils clean .no noise at all but when you drive it 10 to15 kms the oil warning light comes on no oil pressure and the rattles start pull over let it cool start again perfect motor . Always did services new plugs ,oil filter when needed oils clean it's the original motor but it's had 3 gearboxes and 4 rear differentials it's a limited it's got over 450000 kms Australian kms please help don't want to change the motor . How hard is it to do the oil pump? Is it the pump ? And where is the pump in the sump or behind the timing chains any help would be fantastic

 

[Number4]

No other symptoms? On a cold start (after sitting for a while, over night) there's no rattle at start up?

Pump is on the crank behind the chains.

Is it a 4x2 or a 4x4?