Roger,Thanks for the heads up and insight on something I know very little about.Tom. Thanks to you also Madcat.
These are the #'s I found on the rear.If you can help me decode it,I'd appreciate it. 301 / cfd2 / 1369829 That's all I see,and the bigger gear had 37 teeth,the smaller one had 12.Dividing them gives me 3:08.I believe that's how you do it.
:Smarty: Actually, the O axle has an 8.5" 10-bolt ring gear. Their distinctive half-round cover has 12 bolts. The posi units were clutch-type as opposed to the cone-style commonly used in B and P axles. While the O axle is expensive to build, it is relatively strong compared to the 8.2's. There was a heavy-duty version that had 31-spline axles, too. Olds "12-bolts" were produced only from 1967 to 1970. Glenn
Might lay a Type "O"s ring gear next to one from a corporate 8.5, the outer diam is slightly smaller with the type "O". Not 8.2" but closer to 8.3-8.4". Glad you used the " ", as far as calling a type "O" Olds rear a "12 bolt", that's something that has been perpetuated by the Olds crowd for nearly 40 years p The amount of bolts holding a ring gear to the carrier determine what the rear is, not the number of bolts holding the cover. Similiar deal.... On two 8.5 A-body housings I have gone to the trouble of plugging & drilling & tapping the cover area to accept a stock 12 bolt Chevy cover. This "disquise" did not make either of these 8.5 10 bolts into a 12 bolt. After some careful grinding & the cover install, just more cosmetically corrrect to go under two of my 455HO Pontiac A-bodys. In both cases, I did not want to cut the ends off of the original factory 12 bolt housings to weld on tapered bearing ends. Going with the "disquised" 8.5 A-body rears was an easy way to get bolt-in tapered bearing axles. Am def not a fan of c-clip axles, my GT-37 has already had a damaged 1/4 panel from breaking a factory axle at the track, was not that cheap to have the 1/4 replaced Got Posi? :3gears: Roger
Roger, so what is the solution if you have a GM 12 bolt but don't want to cut off axle ends and weld? New axles?
Scott, Good morning. Sure could have gone with new Moser c-clip 30 splines, have done so in many other c-clip 12 bolt builds. Have also ordered new 30 spline Eaton carriers & same exact c-clip axles for 12 sec car 8.5 Firebird rear builds, just prefer bolt-in tapered bearing axles. Basically, for my own piece of mind. Having regular access to a friends machine shop so changing the cover over was rel easy process. Got Posi? :3gears: Roger
Roger,I don't know if you saw this so I'll post it again. These are the #'s I found on the rear.If you can help me decode it,I'd appreciate it. 301 / cfd2 / 1369829 That's all I see,and the bigger gear had 37 teeth,the smaller one had 12.Dividing them gives me 3:08.I believe that's how you do it. __________________
Tom, Hello, the #136 prefix in the hsg's casting number is a Buick number. Later '68-70 BUICK 8.2 rears had a 138 prefix, if memory serves me right. Pontiac cast hsgs of the '65-66 era, should have a number starting with a 977 or 978. 37/12 is indeed, the tooth count for 3.08 8.2 Pontiac ("BOP") ring & pinion used in both Pontiac & '64-67 Buick cast 8.2 rears. Looking at your 2nd pic again, the rear is definitely a '65 or '66 Buick cast 8.2 rearend. If the rear was a '64 model piece, it would have the small "ears" for the '64 small diameter upper control arm bushings to mount into. Your rear has normal sized "ears", single rib on side of hsg, & bolt-on spring mounts so easy to isolate what it is. Hope this helps, Roger
