how to replace oil pump

HOPE! minor repair. lol please check out my analysis in the reply to pushrod's comment

Just curious, how many miles are on the engine?

at idle oil pressure was so low the lifters would rattle. pulled magnetic oil plug and found slivers of metal not just the normal iron sludge. dropped front differential, pulled oil pan. oil pickup tube screen not plugged and o-ring in good shape. dropped splash pan and no discoloration of any rod caps or main journals. no play could be found in any rods. inspected 2 caps and no color change or wear could be seen. replaced caps, not suppose to reuse rod bolts but did, torque to 15 lbs 1st, then 65 ft lbs at mechanics advise since i don't have a degree tool. book says 80deg. removed harmonic balancer, timing cover, and oil pump. looks in good shape. made a call and was advised that gm 6.0 ltr seldom have rod and main bearing, sometimes oil pump, but generally cam roller and lifters. inspected cam from lower end and did note normal narrow wear patterns on all lobes except the 2 rear cylinders. wear pattern nearly covered whole width of one lobe and the other 3/4 of width. the engine didn't rattle while running but when the oil pressure was low, if you listened very carefully, you could kind of hear a rattle that seemed to come from the lower rear area.

I know sometimes on this engine family, the pressure relief valve plunger can stick down just a tad and let the oil just loop back into the pump body. Did not realize you were that savvy! No way to know at first of course. Just replace the pump i say. The reason i ask about the actual pressure test and engine noise is these oil sending units give some problems!

thanks for your help, i won't rule out that the relief valve wasn't stuck, it was a little cruddy. those little slivers of metal on the plug came from somewhere, perhaps valve caused the other damage. i appreciate everyones help. now i just have to decide whether to repair motor, replace w/use or new, or sell it.

65 ft/lbs on the rods?? That's too tight! Whatever you do get the new bolts and torque them correctly!. Besides TTY (torque to yield) bolts will fail without warning if over stretched that's why they are throw aways. A loss of oil pressure that results in lifter noise at low speed quite often comes from wear in the cam bearings. If you don't see anything else, you end up there by default.

you are totally correct on discarding used rod bolts. 65 lbs was advised by a mechanic that overhauls these type of motors. he also advised replacing them, but when a customer request he reuse them, that is what he torques to. no warranty, no guarantee. it seemed a little high as most rod bolts are 45 to 55, not? when i mentioned lifter rattling, it was when oil pressure was already low. running between 5 at idle and 25 at higher rpm. oil pressure had been decreasing for months, but always above 20 at idle and around 40 at higher rpm. when new 40 to 60. it went 5-20 quickly this last trip. (haul heavy loads all the time.)