When I am first starting out from the truck sitting long enough for the engine to get cold, the engine is really loud alomst sounds like a large fan going really fast. The noise increases with engine speed and after usually 2 shifts the noise goes away and everything sounds normal. I have tried letting the truck sit running for a couple of mins to make sure the oil has warmed up a little. I have a 360 with an auto trans with about 250,000 miles and the tranny was just rebuilt(all fluids are topped off), I just changed the oil to Shell 15w40 since I read it will help with compression on high mileage engines. I also am using valvoline full synthetic ATF+4 for the tranny. Any ideas what this is and if it is harmful or just annoying?

 

thats what they call your clutch fan. it will do that untill it reaches optimal speed. dont worry i have an 05 4.7 dak that does it everytime i take of in the morning wether it is 0 outside or 80 outside.