Shipping was what made me decide to go with someone other than Strange for an axle upgrade...now it's free. Complete Rear End Promotion 2020 - Strange Engineering If you want to upgrade, now's the time, get the s-trac. You'll need a longer drive shaft and maybe a change to your upper control arm. Again, the reasons the 9" is such an upgrade is because it has the 3rd pinion bearing to hold the pinion against the ring gear and prevent deflection under hard load (launch) which leads to whine. Also, the hypoid angle lowers where the pinion contacts the ring gear and adds more tooth to tooth surface area (like a worm gear), meaning there is more meat preventing gear tooth breakage.