Originally Posted by mrtosh
3.7 and 4.7 do have some piston slap that's prevalent on cold start up. Nothing to be worried about as the noise will subside as the piston expand and warm up.
Yep piston slap can happen, they are 0 tolerance pistons that have a coating on the side of the piston and when that coating wears it can give the piston room to rattle a little till things expand.
Typically some clatter on startup comes from the valvetrain. perfectly normal on hydraulic valvetrain with some miles on it, the lifters can bleed down and have to pump back up after sitting.
Either way, its pretty common and normal. Keep fresh oil in her and so long as one of these is legitamently what it is it will continue plugin along for another 100k.