if got a 04.5 with the cummins 600, it has just under
72,000 miles and complety stock until last week when i finaly ripped out the stock muffler and catalic converter, and replaced it with a afe system
i changed the engine oil while i was doing the exhaust and noticed a little oil around the sides of the oil pan, i traced it to the front main, so i guess the seal has went out. its not leaking bad enough to drip yet but it will only get worse. i know *** happens sometimes but does this happen to very many 5.9s
i change oil about every 5000 miles and use lucas oil additive and havent been very hard on it  

what wiil happen as mile rack up, the oil pan bolts will loose their torque and therefore loosen up a bit causing oil to seep just as you have describe. therefore, every oil change, i get a torque wrench and retorque them down, no more leaks  

hey black it might also be the timing cover ive seen a lot of em that leak from there i did a timing cover on a 94 12v recently and it wasnt that bad took about 6hrs but i wasnt workin very hard or steady it could be done in 2 if you wre in a hurry haynes manual says to take radiator out but i did not you just have to be careful with the fan to get it past the shroud bolts on the cover are 10mm gasket set is available from local dealer autozone and checker can get it 2 the dealer had it in stock so i bought it there clean the surface of the timing cover housing and lay a thin bead of hi temp rtv mostly to holdthe gasket in place  put your cleaned and prepped cover up and get a couple of bolts started tighten to spec in a cross pattern  throw in your oil filler tube and fan/ clutch assembly and your done hope this helps