Its a torsen(torque sensing) diff. They are a type of limited slip differential which sends drive to whatever wheels have the most grip. Because it a lsd diff and not an open centre like most conventional diffs it doesnt require tuning with different weight oils or grease. It only requires them for lube.

I dont know if the PCR came standard with them, but my hyper 7 pro came with it standard plus also had a convetional diff with it as a option.

[link=http://www.rcuniverse.com/forum/m_4393570/anchors_4393570/mpage_1/key_/anchor/tm.htm#4393570]torsen forum[/link]