**8.75 drop out third member 489 case 3:91 gears sure grip posi**

Count the teeth on the ring gear,then on the pinion.Divide the number on the ring gear by the number on the pinion and bingo we have a ratio

Yes that is the way to equate the ratio, but the unit is in the car operating still. I haven't pulled it yet and installed the other unit. It was professional built and it had all new components installed at that time and that included and new ring & pinion that is a 3:96 ratio set up with dye. I bought it for 675.00 installed it and have not had any problem with it.