noise in rear of car at initial start up to 10mph and goes away??but isnt there all the time--comes and goes

If you have a 2011 Dodge Charger, then its under manufacturer warranty for...oh...another three years. Take it back to the dealer and let them figure it out

9 times out of 10 the dealership "cant" find the problem until after your out of warranty, have your rear differential looked at

Pretty sure thats an erroneous statement...i know from experience being as Im an ASE/Chrysler certified technician. If you are going to dealerships that take 3 years or 36000 miles to diagnose a concern than you are clearly going to the special olympics of dealers. Furthermore, if you make a warranty claim as to a specfic concern during your warranty and it continues to manifest after the warranty has expired, than it will continue to be covered under warranty...thats the way it works. What per se do you believe to be faulty in the rear differential that will ONLY cause a noise between 0-10 mph and not become louder at higher speeds? Id imagine that if the backlash or pinion depth were to be out of spec than it would continue to get louder as speed increases....just saying. FULL FACTORY CHRYSLER WARRANTY= $0 out of pocket/at the most a rental car bill.

Sounds more like something is grounding against the body causing your intermittant "Groaning" noise.