Im currently running 3.08's and want to switch to 3.31's. I've got the gears but I just remembered that there is a cutoff for what series carriers can carry what gears. Am I good to go ... or will I need a different series carrier ? thanks
I just may have to go to 3.73's to keep youse guys in my rearview Dave ... Look in the feedbAck forum
You can go to 3.90 on the 12 bolt 3 series carrier. I believe 10 Bolt is 3.23 to 3.73 in the 3 series. :TU: :TU:
Dave, I got my info from here:http://www.hotrod.com/techarticles/chevy_12_bolt_differential_install/ Tip 15: When shopping for 12-bolt differential parts at a swap meet, keep this in mind: Chevrolet generally used three different types of differentials for the 12-bolt: the Two Series carrier, the Three Series carrier, and the Four Series carrier. The "Two Series" has little use in a hi-po application and should be avoided if at all possible. The Three Series carrier accepted ring and pinions that ranged from 3.08:1 to 3.73:1, while the Four Series carrier accepted ring and pinions ranging from 3.90:1 to 6.14:1. While there are a number of subtle variations between the three types of carriers, a major difference is the thickness of the gear flange. Two Series carriers are the thinnest, while Three Series flanges are thinner than Four Series flanges. Because of the size of the flange, the carriers cannot be randomly used with ring and pinion sets from the trio of "families" (unless, of course, special gears with custom ring gear mounting surfaces are used. These special gears are readily available from Richmond Gear). Additionally, the Two Series carriers do not have any webs on the top of the carrier. Three and Four Series carriers do have webs.
Kind right and wrong.uzzled: Yes O.E. 3.08 to 3.73 on three series and O.E 3.90 gears fit only four series carriers. But an aftermarket "thin" gear 3.90 fits three series as a "thick" gear 4.10 will fit a four series. :Smarty:
Alan you should go to 3.55 you will feel the half turn.3.08 TO 3.31 not much difference.You still will be able to do your road trips at 75-80mph.
In response to Larry's above carrier ID post... Putting down 500 ftlbs of torque & building a c-clip 12 bolt posi rear don't waste your time with swapmeet 2 & 3 series oem Eaton 12 bolt posi carriers, unless your buying them for the bare shells... they gotta be CHEAP. Decent used functional 12 bolt 3 series posi carriers will easily bring $225-250, but will cost minimum of another $250 to upgrade with HD heat treated 17-10's, thicker spring plates & 400# springs. The oem 18-10 side gears & spiders are brittle, & if not spalled (pitted) today, the brittle oem 18-10 12 bolt side/spider gears will often be the doom of a 12 bolt build when they shatter under heavy torque load. Got Posi? :3gears: Roger
Can't help but get amusement out of those who have yanked their '71-72 8.5 10 bolt A-body rears, to "upgrade" to a stock Chevelle 12 bolt with an oem Eaton posi. Unless, that stock Chevelle 12 bolt posi rear came out of a super rare '69 COPO Chevelle & came stock with HD heat treated spider & side gears & truly HD axles, one has just taken 2 steps backwards. Got Posi? :3gears: Roger
If you don't have the 12-bolt Chevy rear yet, you may want to check out racingjunk.com. That is were my brother got his from and it happened to be 10 minutes away from his house.
