I could be wrong, but I don't think the manual gear-shift is enabled for any wheel in this game, PC or console.
I use a G27 on a PC, and the last time I played with the 80's cars, I'm sure that I couldn't use my manual gearbox, I had to use the paddle shifters, making it just like a modern car, with an 80's skin.
Once again the Codies fail the basics. If you choose to 'simulate' cars which really do have manual gearboxes, then enable the option of using the manual gearbox for those wheels that have them. I am surprised they actually put a gear-shift animation in the game TBH. It's an illogical decision.