When the car shifts from 1st into 2nd there's this thunk. It feels like the car hits this threshold and needs just a little extra oomph to push through it. When the car gets that oomph it pushes through that threshold and jumps forward and you can feel and hear the shift inside the cabin. Vrmmm - THUNK- Vrmmm. When I'm going from 2nd to 3rd or into overdrive I don't have the problem. Something similar happens going from 2nd into 1st but not as bad. Not yet anyway. Any advice besides getting another TCU? They are kind of pricey.