8 3/4 Cases

the 742 case uses a 1 3/4" pinion, and the 489 uses a 1 7/8 pinion. the bearing at the gear on the pinion is larger on the 489, and as such, so is the race and where it presses into in the case. The carrier side bearing bores are the same, so you can use a 741/741 carrier (i.e. clutch type sure grip) in a 489 case, as long as you use 741-case bearings/races. and the 489 sure-grip (cone-type) in the 741/742 case with 489 bearings/races.