Oil pressure problems: 99 Ram1500

First I apologize for the length of this post. I'll make it brief as possible.
I bought a 1999 Dodge Ram 1500, 5.2L 4WD with 99k miles and drove it
for about 2 years without problems. I changed the oil regularly with Valvoline 10W30 oil.
I parked the truck for 1 year without starting it. After this time I checked the fluids, started the truck and let it reach operating temperature. All was normal. Later, after driving 10 minutes (6-7miles) the oil pressure dropped to zero. I shut the engine down immediately and checked the oil. I started the truck after several minutes noting normal oil pressure and drove the truck home.
I changed the oil and filter: Same problem.
I pulled and cleaned the pan, installed a new Melling high volume pump, verified the pump shaft, and cleaned the pickup so that it looked new, inside and out with oven cleaner: Same problem.
I installed a mechanical oil pressure gauge to verify the readings.
I pulled the pan and checked the pickup height. The pickup was tight, and the pump was tight with a gasket. I pulled the valve covers. The smooth black crust on the valvetrain and head concerned me. I cleaned the head thinking the oil was being held under the valve covers and running the pump dry. I had good oil flow to the rockers/pushrods when I closed everything up. Same problem.
I pulled the pan to check if the pickup had ingested anything and applied teflon tape to the pickup threads as a precaution. I pulled the intake thinking the black sludge was keeping the oil there. No problems. With the intake removed I was able to drive the pump with a primer shaft. Oil flow seems to be what I would expect. Oil flow seems to be uniform from the head in the lifter valley and draining properly.
The pressure starts at 70psi(cold) and drops slowly to 60psi(warm) with the high volume pump (60psi & 45psi stock pump). If I drive the truck the pressure drops slowly to zero and stays there. At a 3000rpm+ engine speed, no load, the oil pressure drops rapidly to zero then stay there. I may be hearing the oil pump cavitate or chatter at zero pressure. I assume it is running out of oil but as near as I can tell there is always oil in the crankcase, however it's difficult to accurately check a dipstick with the engine running.
I've tried running 20W50 oil with no change. Crankshaft bearings don't make sense in this case, however I'll check the endplay tonight as I saw on another post. If crankshaft bearings were at fault, why would the pump cavitate/chatter? I've put an incredible amount of time into this problem already. I wanna' drive my truck again!
Any suggestions would be appreciated
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First, throw out every valvoline oil you own. Drain the truck.
Replace all above with Castrol.
My last truck, Castrol was the only brand that prevented rod knock. Also, a mechanic I trust very strongly says that Valvoline oil doesn't maintain viscosity. He's had a couple cases where the customer comes in with no oil pressure. He replaces the oil with Quaker State, leaves filter on. And the oil pressure comes back.
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Christopher A. Young
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Stormin Mormon wrote:

Not trying to be a smartass here ... but if Valvoline is really that bad, do you think Cummins would have partnered with them to create "Extreme Blue"? (It's the oil that Cummins recommends for all of its 5.9L CRD engines).
I realize that the OP's truck is not a Cummins, but still ...
As a side note ... I've had no problem with Valvoline. 50K miles using Extreme Blue every 8K. Pressure is good, etc.
Craig C.
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I'm with Craig. I've used Val for years on all 4 of my cars. Nissan Quest Ford Ranger Dodge 1500 Isuzu Ascender No problem with pressure. I'm a satisfied Val user. Not to knock your trusted mechanic, but other than adding new oil to obtain pressure, what other evidence does he provide you that Val is a poor product?

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That covers it. Pretty convicing, by me.
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Christopher A. Young
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