"Oil Pump
The oil pump design on these engines is a two-speed vane-type pump. Its dual-pressure control enables operation at a very efficient oil pressure at lower rpm, and then delivers higher pressure at higher engine speeds.
At temperatures of 32°F (0°C) or colder, when the engine has been sitting for a few hours, it is possible to have air enter the pump through normal oil drainback. Upon start-up, a short rasp sound may be heard from the front of the engine. It is most often heard during a remote start. This is a normal condition."
Below 32* is BS
It was 72 when I left work and the truck sat for about 9 hours and still made the rattle noise upon startup