torque arm?
 

Can anyone help explain exactly how a torque arm helps traction? I know it holds pinion angle, but beyond that I don't even know what it really does.

With a chassis mounted adjustable TA you can make sure you have a little negative pinion angle for the track. You can buy a trans mounted one that will do the same thing, but from what I understand the chassis mounted one does a better job. Something about being able to adj. the instant center of the chassis better. Do a search, the details are over my head.

Try a search. Injuneer has some great write ups on here.