A couple uf years ago I bought a complete used diff assembly for my 05 for $800. It was a 9.75, with 3.55 ratio and limited slip. It had 75,000 miles on it. I changed the fluid, axles seals and parking brake pads while I had it out. That cost another $150 for parts. A friend helped me and we did the job in my driveway in an afternoon.
2013 STX Scab 4x4 5.0