So I have a bit of disappointing news, my brother ended up taking my jeep to a local shop for the rear axle install because he wasn't comfortable hooking up the brake system. So the shop installed it and took it for a quick test drive, and the rear end was vibrating like crazy. So we went in to check it out and the axle shafts can slide in and out about an inch on each side. So we pulled the diff cover off and found pieces of metal loose inside. The axle has less than a mile on it and was installed professionally. We're contacting ECGS now, hopefully they'll do the right thing a replace the defective axle.
Jeep Grand Wrangler Build Thread: http://www.jeepforum.com/forum/f13/jeep-grand-wrangler-build-1398775/#post13935376