hmmm ( G27 user here also )
May sound like a silly question but are you depressing the clutch fully ?
It took me around 3 months to use my G27 clutch and shift properly in GT6 because i was constantly using the clutch too lightly. Gran Turismo ( as far as i am aware ) has always had this "issue" where the clutch should be fully engaged for the shift to happen. It even happens to me now, from time to time, when i am not paying enough attention.
If this happens to be the case for you, i urge you to keep sticking with it and be constantly aware with your gear changes, to make sure you FULLY press in your clutch every time. Soon enough it will not register in our brain of course, as with all car driving functionality and you will REALLY start enjoying driving with the clutch and gear stick
It's such an excellent feeling when it becomes something that works
I am sure you may well already be very aware of this ( hence you saying you are shifting correctly ) but i thought i'd raise it anyway, just in case. For me, it really was just a matter of sticking with it even when it was making me furious. LOTS of track time in "Free Run", so i had no AI to deal with,causing panic in front of me. Nordeslife 12km(?).
Is your wheel set up on a frame or clamped to a table/desk ? I had most problems when i had to clamp my wheel and shifter to a computer desk. Everything felt WAY too high and the arm/hand movement really unnatural. Like an articulated lorry shifter almost! I eventually bought a proper "rig" set up and my wheel and shifter are fully clamped in ( no chance of movement, no matter how hard i treat the wheel ) and my shifter is now nice and low and in a comfortable position that feels as it should do, like in a real car.
Apologies for the crummy picture...
Also, depends on how you feel about physically modding your G27, but i cannot recommend these two mods highly enough...
GTEye brake pedal mod. Super cheap and super effective:
https://www.gtplanet.net/forum/thre...gressive-brake-spring-mod-for-g25-g27.241653/
Place the GTEye spring into your pedals for a much better feeling brake and then move the existing, original G27 brake spring over to the clutch instead. This puts a little more feel into the clutch pedal, as the the spring is now, a little stronger.
and
The above mod certainly helped me, personally, with the gear shifting in particular. Changing from 2nd to 3rd, or 4th to 5th was usually a problem, in terms of the stick sometimes slipping back to 3rd or 1st or even sticking. This mode helps smooth out the movement of the stick itself and allows for a much more accurate gear shift, in my personal experience.