i have a 82 chevy short bed c10, im doing a 5.3/4l60e swap. just a few things to finish up, today i hooked up my drive shaft and popped it into N and pushed it out of the garage and i noticed when it moves forward, it makes a whining noise, kinda like the noise when your tire is on a smooth surface and you turn the wheel. i did not know where it was coming from so i put the rear end on jack stands and i took the drive shaft off the diff and spun it freely and it only makes the noise when i spin it counter clock wise. i know i dont have fluid it in due to changing the fluid and filter. but i just dont know if this is normal or is something wrong?