I have a strange growl noise on cold start up. It sounds like the belt but thats new. It only happens once and than I dont hear it the rest of the day unless it sets 6-8 hours. The truck is a 99 F250XLT crew cab 4x4 auto with a 5.4. Its a great truck but the sound bothers me. thanks to anyone who has a cure

 

It could be your fan clutch. When cold, they lock up and draw huge amoounts of air. It's normal.