Its a much cheaper alternative than buying a billet case for people making a good chunk of power. It helps prevent the trans case from parting/cracking.

 

Im surprised no one makes a billet outter case

 

I thought they did? Maybe the weak link is just the inner side?

 

No billet outer for a stock based trans. Most of the forces go through the innerncase "bellhousing" for you other folk lol

the strain of the clutch assembly/power on the input shaft plus the force of the throwout bearing, etc. A lot of the twisting forces center on that inner case. Especially on hard launches, strainful drivetrain conditions (wheelhop, control arm movement, rev matching downshifts repeatedly on road course, then back to full throttle, etc.) If a component were to give it would be the inner trans case (and it has) Not to mention if a clutch component were to fail, the billet case has more "give" or stretch, so the likely hood of a catastrophic shrapnel throwing event is reduced, even more so if using a scatter shield as well.