posy traction
 

i have taken the rear differential out and took it apart. i locked up the gears inside to make it a posive traction differential instead of a limited slip differential. givs it a better jump off the line and the wheels spin simontaniously. not really healthy but it is affective.

sounds liek a useful mod... do you get better drifts or powerslides?

Actually the ball rear diff is more like a posi. (and a little like a slipper clutch if it's loose)
If you want to make a locker- like a solid axle, use silly putty.

Open up your gear diff.
put a small ball of silly putty on each gear
squeeze it closed, and your differential will be locked solid.
This will help more for drag and straight line. It will make the car skid around more, and I guess you could call that drifting, if you want to.
The best part is that you can take it apart and remove the silly putty, unlike glue or epoxy.

is the ball diff. hard to take apart? i have also known people to sick paper in it. does that work or does anyone know?

the ball diff is the same 3 screws as the regular diff, but I don't want to go chasing all the little peices down. Plus, you should have and extra geared diff, because that's what it comes with stock.
anything can be used to lock it. I just use silly putty because it's easy to put in and take out. Paper would also be a good solution. anything to keep the gears from moving.
You can also use thick heavy grease- that will give you a little differential action but not much.