i want to change my 12 bolt 4:10 gear to a 3:73. rick's has a 3 carrier series gear. is that what an original 12 bolt has. thank you. also what else if anything do i need to do the swap?

If your 4.10 gear is factory installed then you will have a 4 series posi. You can get a thin 3.73 gear that will fit the 4 series. If it was not factory installed then you may have a 3 series posi. If this is the case then a standard 3.73 gear is what you need. Either way, you can get the gear that you need. You must find out which series posi you have before you order a gear. The posi case will have a casting number on it. The number will be next to the bearing on the side opposite of the ring gear. The 3 series is EDB-30140 and the 4 series is EDB-30174.

it is not a factory gear i beleive it was a stock gear but the fellow that owned it originalyput the 4:10 in to go to the track on weekends. so in that case i should find the 140 #. thank you for your help. barry