wierd sound

ok guys, this is kind of hard to explain, i dont know if this a natural sound on tahoe's. I have a 5.7L Lt 4wd. i bought it not too long back and it has done this since i've had it. When i start off from stop, there is a shifting/sliding sound in the back of the vehicle. i was wondering if the leaf springs shifted, and if they did could i fix the sound by just oiling my leafs? or does this have completely nothing to do with the sound. The sound itself doesnt last long, its pretty much instantaneous, but sounds like a metal on metal shift. all info is welcome, and thanked

Its probably the infamous "Clunk"......lots and lots of hoes do it. I believe it has something to do with the slip yoke.