Is this noise there all the while the engine is running? Even in park?
If so, remove the ABS fuse (60A) from the underhood fuse box to see if the noise stops. If so the ABS pump "motor" is running at all times.
Now with engine running (in park) try hitting the brakes to see if the engine dies. Post your results here for further assistance.

is the alternator working??

what is the voltage at the battery when running??

Roy

the voltage at battery when running is at normal 14v, but when brakes are applied it drops to 6v then goes dead. i havent tried removing fuse yet, raining hard here in texas, but will try it asap. if it stops the roaring do i need to replace the ABS pump motor?

only when the truck is in drive and moving is when i hear the noise

when in park, i apply the brakes the voltage drops to 8-10v but doesnt go dead