Yeah mine wasn't humming. I had to tolerate a very loud and obnoxious grinding noise and over a 1/4 inch of play in my diff on a manual while it also helped kill what lil gas mileage i already have.

Currently have a gain of 8mpg since the change out. I get to hear my baby purr now. I remember why i bought her. Driving a manual with a bad diff sucks though. Causes the truck to rock and sometimes a nice knock into gear. But that's all gone now so i'm happy. I'll be happier when i can see straight back out of my rear view mirror to. As well as jumping the truck across railroad tracks vs. having to slow way down.

 

flipping the shackle mounts according to my measurements is about 3/4 of an in raise and then the extra 2 inches from the new shackles should put me within where the old rear end setup was.