guys i was wondering if you could tell me if there is a way to ID a 8 3/4 rears gear and if its a posi with out taking the thing apart? junk yard shopping can be tricky!!!! if you know what i mean!!!
On the center section housing (pig) directly below the pinion you'll find a casting number which will end in either 741 or 742 or 489, these are all good rears. If it ends in 657 you don't want it. The quickest way to tell if it's got a sure grip (posi) is turn one axle and if the other axle is turning the same direction then it's a sure grip, if turns in the other it's open. Gear ratio is turn the pinion and count how many revolutions it turns when the axles turn 1 revolution, eg. if the pinion turns 3 1/2 turns to one turn of the axle it's a 3.55 to 1 ratio.