There's actually no problems with the 705 rear diffs. The only thing was that like the NTC3, you could not adjust the ball diff on the fly. You need to loosen the grub screw which is difficult to access. Else, if you try to loosen the rear diff externally without loosening the grub screw, you'll end up with the rear end loosing drive.

There's a simple solution to that which is to use loctite. There was some instructions compiled with regards to building a bullet proof ball diff posted on the 705 thread. One that would make the ball diff able to adjust externally even without the use of the external diff adjuster hop up.

I further went ahead to use the FPS pulley on the normal ball diff because that one protects and closes the diff balls better. Also, not that it's a serious problem but it takes away the wobble found when you install the stock pulley. And yes, lastly the FPS diff pulley is wider and does not make the rear belt slip like what some people have complained...