Truck Repair: 1999 dodge 24 valve cummins automatic trans, oil pressure gauge, oil pressure sending unit

I have a 1999 dodge 3500 with a 24 valve cummins everything seems to be working fine but the oil pressure gauge will go up to 40 lbs then flutter from 0 to 40 for a few second wen u drive then it just stays at 0, I'm not to diesel knowledgeable but know a lot about gas vehicles if u could help me out that would b awesome thank u.

first thing you should do is pull a plug out of the main oil galley and install a manual gauge to make sure it is keeping oil pressure up.If it is its probably the oil pressure sending unit,if it is not holding pressure it could have a problem wiyh the pick up tube or a bad oil pump.