all right...i've got one that i haven't heard before. only under acceleration do i hear this popping/clunking sound. i think it's either coming from the u joints or maybe even a loose chain in the transfer case. i'm gonna drain the transfer case sometime soon to see if there are any chips in the fluid. when in the driver's seat it sounds like it's coming from the rear, and when i lean towards the rear it sounds like it's coming from the front. that's why i thought it might be a loose chain. any thoughts on what it could be other that that? oh it's a 98 4.0 5spd with 183xxx. so i figure it's about time for stuff to wear out.