i just bought a 2002 4.7 2wd durango it ran fine for a few days then it started having some intermittent trouble in overdrive, sometimes it would work fine sometimes it made a horrible sound in overdrive so i just turned it off, then reverse started popping and jumping while backing up then it started grinding terribly now doesnt grind at all in reverse just wont go.... what the hell is going on? do i need a new tranny? car has 180k but others wise runs like a top

 

Being that it had some grinding going on and now no reverse, i would say its time to look for a good transmission shop.