a broken spur gear is from gear mesh, take a pice of notebook paper and put it between the pinion and spur, move the pinon sug up to the spur and paper just tight enought not to break the paper, tighten the screws down and then spin the spur gear by hand to remove the paper and as long as the paper isnt torn or broken you should have the correct gear mesh.
as for the sliper you would want it to slip for one or two feet i belive on my losi i have it tight because i race stock.
so your just taking away the slipper, thats not a locker, a locker is in the diff. when the axles are "locked" together meaning each wheel gets 100% of the power from the trany (aside from any loss from the slipper slipping). i dont think you would realy want to run a "locked" diff on a t3 that would just make its handling go out the window.