Originally posted by COBM:
this is a message from quaife
First and absolutely most importantly, the Quaife differential housing is manufactured from billet steel while the competitor's unit has traditionally been a cast housing. While a cast housing suffices in OEM applications where the power will not be uprated, in a high performance or racing environment the stakes are much higher. Any significant power upgrades will increase loads and forces and eventually break a cast housing as the stresses put on the housing are too great. Those of you that are metallurgists should be able to confirm this to be true.
Well, I am a metallurgist, so I've got to chime in here. Obviously a cast structure can have unwanted defects in it (porosity, non-uniform grain structure) and doesn't have the benefits that a wrought structure would have. I am assuming that, when he says "billet" that he means that the steel has had some sort of hot or cold working operation to refine the grain structure, seal porosity, etc. Note also that "billet" can mean steel with a cast structure-many steel mini-mills will continuously cast 5" square cross sections and call them billets.
However, if a casting is designed properly for the application, it can be quite sufficient. The turbine blades that are spinning at high rpms in jet engines are castings. Granted, they are incredibly advanced single crystal castings where all the atoms are lined up in the same orientation throughout the entire blade, but you get my drift.
Obviously I don't know why Torsen's engineers decided to use a cast housing, but I would imagine that they took into account the fact that people might be buying a LSD because they performed "significant power upgrades". Predicting that a cast housing will fail because of the stresses put on it without knowing the magnitude of those stresses is out of my ballpark. I'm not trying to rip on Quaife here, just trying to provide a little insight.
Hell, most of us drive around on CAST aluminum wheels without problems.
