I changed the differential fluid last year. When I put the car into reverse I get a nice clunk on occasion. Sometimes not at all. I almost want to say I feel some "play" or something when selecting reverse right before the clunking sound. I was thinking it could be a transmission issue but I remember reading somewhere that a reverse clunk could be low differential fluid??? Maybe I didnt get it filled all the way up? The differential is filled until it comes out of the fill hole right? I cant remember. Its one of those deals where you cant "overfill" it because once it starts coming out the fill hole you put the plug in?