[KevinP73]

I've got a 2000 Dakota with a 4.7 automatic 2wheel drive. The engines has 198000 on it. Rebuilt at 146000 and it's been trouble free since then. Recently I noticed the oil pressure gauge doesn't show any more than 40lbs at speed. Now here's the mystery. Lately the gauge will drop, at idle or after a sudden deceleration, to 0lbs and the "check gauges" light will come on. It will most often regain pressure once I accelerate again. Sometimes it doesn't. Checking the oil shows I'm full on the stick. Even when running with no pressure indicated there is no change in the sound of the engine. I'd expect some noise if I were running 60mph for ten minutes with no oil pressure at all. I've replaced the pressure switch but that didn't change anything.
What do you think the issue is?