Originally Posted by BA68 mustang
Okay but I'm concerned with putting shorter gears in it because it's a c4 and it's goanna be my dd if you will (I'm only 16)... Sorry for being so questionative
There are phone apps and online formulas for calculating your rpm's at 70 mph, for example. You can figure where you are now and then plug in rear end in the low 3's ratio and see how much your rpm's go up, which should give you an idea of how it will affect your fuel consumption. You just need to know you tire height, rear ratio and the speed. I will help to decide if you want gears or what ratio will be best.