RAMBOW

Been watching this on the local craigslist. Pretty cheap now.

http://seattle.craigslist.org/kit/pts/2553120711.html

But i'm confused about which the "good" Type "o" rears are.
Am i correct that there is a 12bolt/10bolt that has 8.5" ring gear, and there is a 10bolt/10bolt that has 8.5" ring gear.... And there are 2 totally different 12bolt/10bolts & 10bolt/10bolt that has 8.2/8.3" ring gear...

Is that right? can anyone clarify how i can tell if this is one of the desireable ones w/o actually opening it up and measuring it?

halfmoontrail

Most people don't like the Type O rears, but I do. This is a "good" one, unless you want posi or a different gear ratio...if so you'll have some searching to do.

The Type O has a 12-bolt cover and a 10-bolt 8.5" ring gear. Pre-71 BPO 10-bolt cover rear ends have a 10-bolt 8.2" ring gear; and post-71 10-bolt covers have a 10-bolt 8.5" ring gear...often called the corporate rear end.

Steve

RAMBOW

I do want posi & different gears. Are they not available?

monzaz

Well - The 12 bolt 'O' type rear really in MY measurements is 8.4" diameter - I prefer NOT to call it a 8.5 like Summit and other HOT ROD shops do- IT JUST CONFUSES PEOPLE - This is the perfect example

10 bolt 8.5 ring gear diameter BIA is in 1971 1972 cutlass only
12 bolt olds (8.4 12 bolt cover 10 bolt ring gear BIA) is 1967-1970 only
12 bolt chevy (8.875 ring gear diameter C-Clip axles)

Aftermarket gears from RICHMOND are available (3.42 and 3.90 and if you can find them 4.10 also) THESE gears are made to fit the 3 series carrier (3.08 3.23 carrier)

POSI unit are available also from reconditioned units to new to Eaton type to true trac. The later ones are getting very expensive BUT at least they are offered now.

12 bolt olds 67-68 rears did come with performance options 31 spline carrier and axles combo for the HIGH POWERED cutlass in the day W-30 etc.

PM me if you need to talk personally on options if you do by this rear. Jim

JD

Fakser

I can't read the letter or number next to the S on the axle housing. could be 2.73 up to 3.42 open or posi. If you can find out the digit next to the S you can find out the ratio and open or anti spin status.