Like the title says. I am looking to buy a 3.91 diff here locally in the midwest. I snapped my pinion in 2 last friday @ the drag strip. The car hooked good for 1 run & made the best time in the car yet. Tried to leave harder & the pinion snapped off right @ the pinion flange. This was with a solid pinion shim. Any help or leads is apreciated guys thanks.