Hey man, I had a 98 3.9 with the same problem. I bet you're using a fram oil filter, am I right? try using a bosch. Frams are the worst filter you can buy next to stp, which coincidentally is made by fram also. 10 to 1 says that fixes the problem. I also switched to full synthetic and that helped as well.

 

Sounds like a mechanic that wants to charge you for a rebuilt when he will probabaly put straight 50 racing oil in it and the oil pressure will stay up ALWAYS

 

yeah....."its a shot in the dark to replace the oil pump, so lets try to rebuild the engine first." I would deffinatly find a different mechanic. And replace the oil pump

 

Mine was doing the same Low oil to NO oil pressure at Idle when warm..Went out and got a Mellen HV pump..Dropped the pan and found.....WORN OUT ROD BEARINGS allowing excess oil to drain away at idle.. caught it just in time.. the fix ( Rod and main bearings and HV pump ) cost me $575.00 (mechanic installed labor included)today and I was happy as all getout that I didn't wait and spin one of those bearings or worse yet- sieze the engine in the middle of nowhere.

 

I read all of the threads and decided to get an engine flush and high mileage oil. So far the problem is gone. The process helped a similar prob wth my Passat. The Passat was notorious for sludge. Passat is running strong. I will post the progress with my 99 Ram.