The 10.5 has a helical gear type differential. A new 3rd party is $575. You most certainly would want to replace the bearings and probably the ring and pinion too. Did you change the differential oil. If something broke which it sounds like it did there would probably be signs in the oil. You might be able to pull a complete axle from a junk yard for less but you will not know what condition its in either until you open it up.

 

Thanks. Totally missed that