I got a ML430 With transmission issues. It will not drive forward just revs when I hit the gas. It will go into neutral and Reverse, I can hear it, But not drive. The Code reader detects P0715 so I replaced the conductor plate but I have the same issue. Well before the new conductor plate it did not reverse.

 

Please UPDATE YOUR PROFILE in USER CP to include the hear and where you live.

 

You probably did not engage the selector valve arm. Now you will have to do it all over again & hopefully it is not damaged.