1406 4 pole 4600kv

I sure hope someone has a suggestion for me. I just installed a new Castle Creations 4600kv 4-pole motor in my 2wd Slash. At the same time I changed the diff fluid to 50,000wt and change the gearing to 18/86.

On my test run in the street it pulls very aggressively to the right (to be honest now that I'm back in the house I can't remember if it was left or right) when on full power. I mean it will sometimes just spin out because I can't counter steer it enough. Especially from a stand still. Clearly one of the wheels is getting more drive than the other, but why?

I've checked the wheels and drive axles and nothing seems to be binding at all. There are no weird noises either.

What could be the cause?

I hate tearing into the diff on this truck. You have to remove so much to get to it. Otherwise I'd investigate, but hoping to get some clear suggestions from people who may have experienced this before I open anything up.

ben