How much gain with lower gears?

Your won't know till you run a back to back test, but odds are, you won't see much difference going from 3:23 to 3:73 with your 408.... I have ran a 3:55 gear, swapped in a 5:13 and the car ran the EXACTLY same et
this sounds a little weired. maybe a bigger traction problem w/ lower gears ? car not set up right?