On my 08 Charger Daytona I have for quit some time now a shudder or a hard thump in the drive line when decelerating. While moving above 25 mph and taking my foot off the gas the engine drops to idle rpm but the drive train produces a heavy thump as if I downshifted to low. This was an intermittent problem but now it is common. After 40000 miles this is the only drive train problem that has occurred. The 5-speed gets a lot of knocks but the one in my car is set up perfect for performance and economy. The shifts are quick and keep the engine in its power band. The slap stick shifter(old school) is a blast to use because it lets the engine work up to its red line. Since the mechanical condition of the transmission seems to be 4.0 makes me think it needs a little tweaking with the programing. Hasn't set a code so the dealership doesn't have a starting point.