Check to make sure the trans and motor plate are connected correctly, and then the slipper is seated correctly on the top shaft. Its possible the top shaft or motor plate is bent too.
Now on to my rant.... not just for this thread, but in general.
I never understood why people make such a point to tell everyone how much money they spend on their RC cars, and that this is a hobby only for the high rollers. Cmon, really? And someone said this isn't a hobby for 14year olds? I think that's exactly who the hobby should cater to.
It should be about the fun, not how much money you can say you spend. Sorry to break it to you guys, but if you want to impress people, spending more than the next guy on RC cars isn't the way to do it. But if you have really expensive RC cars, AND a really nice comic book collection, then people will be impressed. (/sarcasm font)