Why does my 2001 Cheve Silverado 5.3 L make a knocking sound when started cold and then go away after it runs a minute or if it is driven a minute. The sound seems to come from the bottom of the motor or the tranny area and has been there since i bought the vehicle. It doesn't seem to be getting worse and someone suggested piston slap as the problem. Any ideas ?
The fluids are good and the tranny is rebuilt too.
