Toyota reports that some 2011-13 Scion tC coupes with 6-speed manual gearboxes may emit a growling or rattling sound from the transmission area when the clutch pedal is fully released.
One probable cause for the noise, says the car maker, is a prematurely worn input shaft rear bearing.
Swapping in an improved design unit with radial ball bearings, part #90363-35068, should eliminate the noise immediately.