My new ML acts very wierd when it shifts gears. When I slow down to about 5 mph and speed up again, it makes a thud. The car also feels like i ran into a curb for a second. this happens when I'm going pretty slow such as in areas like parking lots.

 

you got the latest model and it's worth taking it back to the dealer for check.

 

If you goose the transmission at a low speed while slowing down, it will slam the components back and forth as the slack is being taken up from the the wheels driving the engine to the engine driving the wheels; and often while the transmission was about to make a gear change. Any Ml will do this. I can induce this condition as well, but choose not to do so. This is a 4x4 (of sorts) and there are a lot of mechanical pieces moving around down there. Continuing this practice will probably damage your (very expensive) transfer case. I don't think there is anything wrong with your ML.