My G6 is a 6 speed manual. Problem is at times I cannot shift thru the gears. Other times it is just fine. Car has a recent HD clutch kit installed.

My clutch foot is on the floor and it acts as if clutch won't release. Have to turn car off , put in gear and then go.  At times it shifts perfectly with no problems. 

Stop at a stop sign and it will go but very difficult to change gears.

Thank You, Butch

I'm not all that familiar with the G6.  Hydraulic clutch or cable?   Was the throwout bearing changed when the heavy duty clutch went in?

Rick

Hard shifting is usually caused by the clutch not releasing. The most common cause of this is a leak in the clutch hydraulic system and low fluid. I would check your fluid level for your clutch and also check to see if you have a fluid leak.

i suspect something was not done correctly when you had the clutch kit installed or the system was already low and no one checked it.
 

Another but less likely problem is that the hydraulic throw out bearing may have over expanded by too much clutch travel (e.g. hydraulic pressure) and it has distended or distorted in some way and may need to be replaced.