When I put on a Fully Customizable Transmission Dog Clutch, my H shifter does not work at all. I'm currently using it on mt subaru at the moment. Any susggestions? It works if i have the stock tran and 6 speed trans.
I don't remember if it applies to all cars, but once you put on the Fully Customizable Transmission you cannot use the H-shifter; paddles only. It's just another one of the quirks in Gran Turismo.
There are even exceptions to this rule; the Mercedes C9 had an H-pattern IRL but it doesn't work in GT6. It's mainly the standard race cars that have issues unless you upgrade non-race cars to the FCT.
I think there are more examples of premium race cars with the issue. The McLaren F1 race car(s) might not work. It's been a while since I drove them.
I find the H-pattern issue is a random thing in GT6. Many standard race cars actually have working H-patterns. The older Nissan GT-R and NSX race cars work. Even the Nomad Diablo works.