I tried to mod my 6th gear on my fully custom transmission and I loaded up gt5 and nothing I tried again nothing. Any tips on how to get it to work?
i never needed to mod a gearbox so i can't help you with that.
did you try to swap a gearbox from other car and mod it?
i have a Shelby GT350 with Amemya RX7 gearbox so gearboxswap works.