The knocking sound gets faster as actual speed increases, not engine speed. It's definatly coming from the rear of the car. Any idea what this could be??? It's not real loud, but it's loud enough to notice and i dont want my diff to lock up or break or anything...

Please help.. thanks

 

Oh yeah, I forgot to mention... it's only when your on the gas that it knocks. For example, if you take your foot off the accelerator to coast the knocking stops.