Maybe lifter tick or piston slap

[Yukon2000xl]

So even though this 4.8 has 46000km on it ,it has an annoying sound on start up .It sounds either like a lifter or piston slap .It stays that way until I rev the engine then it’s gone not a sound afterwards.Until i rev the engine it just stays there .I dumped a liter of ATF in to see if I can clean the lifters out but the oil literally looks transparent on the dipstick prior .Can my lifter be dry because it doesn’t hold pressure and when I rev it the lifters relube? Also does that O-ring in the pickup tube have anything to do with this ? All in all the oil pressure never moves in the low range and only goes upwards at higher speeds.

Thanks .


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[PNWYukon]

Lifters have been known issues on many of our vehicles. Usually, though, the noise is normal on the 5.3, not sure about the 4.8. If the noise goes away then it sounds like lifter/lash adjusters. Unless you have accompanying issues it seems to be normal. Maybe someone with 4.8 experience will chime in.