I have a 2001 Sub 2500 w/ a 6 liter engine with 185K. I have owned since 162k and when I start it up it will knock for about 30 seconds then it quits. The oil pressure is normal when the knocking occurs. It has done this since I have owned it and does not seem to be getting worse. Does not happen when engine is warmed up. It uses about half a quart of oil every 3000 miles.

Does anyone have any ideas? Am I looking at a rebuild soon?

 

I have a 98 K1500, 5.7 Vortec. Since the last oil change it does the same thing, I think. There's a nasty little knock at start-up, but 15 or 20 seconds later it's quiet and all good. I think it's probably a wrist pin, or maybe a top ring land, since it's quiet all the rest of the time and the rods or crank bearings don't hammer after an oil change. If I keep it under extreme RPM's I think it won't have much impact.