slow knocking noise coming from the back(possibly from the trunk) of my 2007 E350, I had it looked into a couple of times at the dealerships, I still have the original warranty. I was told from the tech didn't hear anything to it could be the purge valve. I had an accident the hood and the bumper were damaged there was very shoddy body work done(that story continues). Approximately one month later, I'm hearing this knocking noise that seems to be coming from the back, like something was under the car, I checked and nothing was there, I had just filled up, but already had slightly less than half a tank of gas. I checked the oil, it's full. The car doesn't make this noise in idle or when I rev the engine. The noise starts upon acceleration, and continues until I drive at about 60. This noise just happened suddenly, I'm wondering if it could be from the slow knocking noise I've been hearing over time and it's escalated to this rapid knocking noise. I just had a recall for transmission bushings around a week after I picked the car up from the body shop. I custom ordered my car from the dealership, even though it's been almost 2.5 years since I bought her, she was purchased brand new. I don't understand what could be going on, I certainly did not expect to have any problems of this nature being the age of the car, she has about 33-35k miles on her, and yes I do, do a lot of driving!. Thanks for any and all help, I will be taking her in to get checked out, I would still like any opinions , and to possibly be given a heads up due to expertise opinions, and or personal experiences on anything related to anything and or everything I've written.