When it is cool the engine starts up and runs good no noises. Even after the initial high idle at startup there is no noise oil pressure good. After a while of driving when at lower RPM's the oil pressure gauge drops and the engine begins to knock. You start driving oil pressure goes back up and no noise.
Oil Pressure on 1995 Ford Bronco
Don't drive it until the oil pump has been changed as this same thing happened to my 1990 Bronco 5.8 and Ford replaced the engine under the extended warranty and you can get a estimate here for oil pump replacement www.repairpal.com/estimator and locate a repair shop here www.repairpal.com/directory
This is a bad oil pump. 5.8 is a bear to replace because the cross member is in the way to drop the oil pane down. Very few cases you can unbolt the motor mounts and raise the motor gently up. The pump pick up screen is likely gunked up but if you go through all the trouble to take that out to clean it and you don't change the pump while you are there, you are cutting off your nose to spite your face as they say. One thing is certain , you will cause expensive damages to your engine if you don't react. Good luck! Joe R.