Seeing how I have an automatic, I am posting based on heresay...
But don't many new cars, as well as the Sonic, have a "retainer" under the knob, that you have to pull up to put the car in reverse so that you dont accidentally shift into reverse at speed?
My buddy's 2006 Pontiac G6 GTP, 6 speed manual has this, and as far as the information he has found says, he can't change his knob because of it.