Truck Repair: cummins L10, oil pressure gauge, cummins l10

Question
I HAVE A 84 INTERNATIONAL DUMP TRUCK BOBTAIL WITH A CUMMINS L10. IT IS MAKING A LOUD CLUNKING NOISE AND RUNS REAL ROUGH, IT ALSO HAS NO OIL PRESSURE SINCE THIS STARTED, I HAVE PULLED THE OIL PAN AND DO NOT SEE ANYTHING WRONG, THERE IS NO METAL IN THE OIL AND THE OIL WAS CHANGED IN THE LAST WEEK. I CHECKED THE RODS AND CRANK AND THEY LOOK OK NOTHING IS LOOSE, THERE WAS NO WARNING IT WAS INSTANT, WHEN THIS HAPPENED THE TRUCK WAS MOVING VERY SLOW AND NOT UNDER A LOAD OR BEING OVER REVED.THE TRUCK WIL STILL START BUT THE OIL PRESSURE GAUGE DOES NOT MOVE WHAT DO YOU THINK COULD BE WRONG WHAT WOULD BE MY NEXT STEP AND DO YOU HAVE A MANUAL ON THIS ENGINE, I HAVE TRYED TO GET ONE BUT HAVE NOT HAD ANY LUCK. THANK YOU

Answer
If you truley have no oil pressure I would mainly look in the bearings.  Before tear down I will usually install a known good oil pressure gauge direct into the oil passage to make sure the gauge in the dash is accurate.  I would pull each rod and main cap off one at a time and check the condition of each.  If it wasnt ran very long with the "cluncking" than sometimes you get little to no metal in the pan.  Also check to see if the piston oil jets are intact(small jet in the side of the block that points upward to cool off the pistons) if they break or come loose the oil will dump directly back into the pan and give you no oil pressure..  We get our books from our local Cummins dealer, not the cheapest in the world but they are good books.  I hope this helps and let me know if you need further assistance.