all what i know that the optra have 1.6 and 1.8 and 2.0 liter engines with different gear boxes according to the engine power and what i know also that the daweoo ( Chevrolet ) engines and gear boxes was developed with technical support from Opel (also GM partner) but the gear box of optra is not same of nubera, cause nubera was a an exception from the cooperation with opel, but any way the optra is not a bad car, i think it is good car