[bradley fideldy]

what is the difference between the different series numbers for rear end posi's. Guess my basic question is........i have a good deal on a 12 bolt rear out of a 65 .....it has 3:07 or 3:23 gears........and i have them taken out and put a 4:10 posi unit installed ? or do i need to find one with something with lower gear ratio to begin with?

[bradley fideldy]

bump

[Karch]

You have a series 3 carrier. Whether or not it's a posi, if factory gears, and no spacer, than you have a series 3.

If you buy a new posi carrier, than you can call your shots. Series 3 or 4.

[Matt Meaney]

3.07, 3.31, 3.55 gears are used on a 3 series carrier. 3.73 & 4.10 gears are used on a 4 series carrier. richmond gear makes a "thick" 4 series gear to fit the 3 series carrier without using a spacer. sooo, if it's a posi now, you can just swap the gears to 4.10. if it's open and your changing to a whole different carrier, just match the carrier to the gears you want. the rear end housing will accept any aftermarket gear no matter what it came with from the factory.

they also have kits to change an open carrier to a posi. this is a 12 bolt rear, you've got so many options it's not funny.

go onto the richmond gear web site and have fun!

[D. Miles]

Matt, just a little correction... 3.08's to 3.90's are all three series gears and can be used on three series carriers and and two series carriers with a spacer. Richmond does make a "thin" ring and pinion 3.73 gear to fit a four series carrier (mainly designed for guys with spools since spools only come in four series and guys wanting to go from 4.11's and 4.56's down to 3.73's for more streetability) and "thick" (spacer built in) ring and pinion 4.10's 4.56's and 4.88's to fit a three series carrier. If you can get one each of a two, three and four series carrier and stand them on end you will see the 1/4 differance of the ring gear mounting flange. The two series carrier flange is closer to the left side carrier bearing making the ring gear further to the left because if you have seen the pinion gear from a set of 2.56's, we call them the sun flower gear because they are huge, the ring gear would have to be moved further back for room of the larger gear (numerically lower gear ratios would have more teeth on the pinion gear therefore makes it larger). The four series carrier ring gear flange would be closer to the center of the carrier or more to the right because the pinion gears is significantly smaller due to the lower amount of teeth like a set of 4.88's which have only 8 teeth on the pinion and 39 on the ring but a set of 2.73 would have 15 teeth on the pinion and 41 on the ring. So no matter which carrier you have as long as it is a posi carrier, you should be able to find a gear ratio to fit you needs. If you have a two series carrier and want to run a three series gear you will need a spacer if you want to run a four series gear you will need the four series gear that is extra thick to fit a three series carrier and use a spacer. I f you have a three series carrier 3.08, 3.23, 3.31, 3.55, standard 3.73 and 3.90 gears will fit with no spacer and again the extra thick four series ratios (4.10, 4.56, and 4.88) will fit and 4.10 to 6.14 gears with a spacer will work (5.14, 5.38, 5.57, 5.86 and 6.14 require a special cross shaft). If you have a four series carrier of couse all the four and five series ratios will work and the special "thin" cut 3.73's will work, all with no spacer... Hope this helps. Thanks D. Miles

[Matt Meaney]

D. Miles, i sit corrected. thank you.