My Estarter came with D gearing, so you're good to go with that and all the other parts.

The only thing that I've heard complaint about is the battery pack. The 400's tend to be a bit more amp hungry than the 300's and that pack, which I am assuming is a GWS pack, can't deliver a full amp meal for the motor.

There is a thread at rcgroups.com regarding that pack between me, some other flyers and a GWS representative. If you really, really, need the link, I can try to find it for you. Nothing there that I haven't said here, but some people just like to read!