['ol Pinion head]

If you guys haven't seen a bolt-in axle 8.5 you haven't been paying attention.

Subject of the oem corporate S spring posis. Think all of us would would agree, the stock 28 spline S spring posi's have there limitations, that's one of the reasons I took exception to George's article. Why gamble with something that has strength limitations & one cannot get even maintenance parts for (clutches, clutch shims, new side gears)? Built with a 30 spline HD Eaton clutch posi & a pair of bolt-in Mosers, the 8.5 rear can be built extremely tough. Properly rebuilding an 8.5 S spring posi carrier, properly shimming the clutches up, & making do with it, then later needing to replace a shelled S spring posi carrier & often a damaged ring & pinion is where a lot of money can be spent. Cliff, I've seen your scenario several times.

To buy a Moser's musclepack bolt-in axle 30 spline 12 bolt rear with new 30 spline Eaton carrier, 1310 u-joint flange & have it shipped in one is looking at nearly $3300. yeah, you get new drums & loaded brakes.

Carefully buying parts, one can reuse their brake drums & brake backing plates & build two HD 8.5 A-body rears with Moser 30 spline tapered bearing bolt-in axles, quality gears, timken bearings, new HD Eaton carriers, and a 3R u-joint flange (bigger than Mosers musclepack spicer 1310) for same money. Can it have 33 splines in HD posi form? No, will it hold up, for many street-strip Pontiac's, it's probably overkill. I have a local V8 Buick street car friend whose car's been running a 30 spline 8.5 A-body HD Eaton posi rear for nearly 10 years. Low low 10's on the spray & high 10's on the motor. Mighty tough, all due to design, ie, a housing center section made by the factory with nodular iron, & if one actually studied it, has more pinion support in it than an oem GM 12 bolt. Oh the blasphemy! When built, he had a little over $1300 in it. In 10 years, I've replaced the clutches in the posi once. No need for a hernia inducing install of a aftermarket Dana 60 A-body rear in his car. He doesn't need it. I like Dana 60's too, but they're too d#mn heavy & then factor in parasitic loss. No thanks, only big Dana I need is under the back end of my Cummins Dodge.

Leaf spring rears: HD bolt-in axle 8.5 housing wise from the factory, there is nothing as drop in as there is with the 8.5 A-body rears. On '67-69 Firebirds, they are however, the same width as the '71-72 8.5 A-body rear. It is some work, but stripping off the A-body lower perchs & TIG welding on reinforced multileaf brackets in a jig yields a stock width 8.5 early Firebird housing or 2nd Gen F-body rear.. One can also cut the c-clip housing ends off the 1" narrower Nova 8.5 housing & jig weld on bolt-in axle ends (either new or used A-10 GM ends) then order bolt-in tapered bearing axles. I really like the A-10 bearing end 8.5 A-body housing, but they are tough to find & as housings and have always been used up quickly. About 15 years ago, I ran across a B series GM housing with A-10 housing ends. Out of local crusher yards & Pick-N-Pulls managed to cut off several dozen pairs of A-10 housing ends. After trimming them, putting a bevel on them in the lathe & properly welding them on, the A-10 ends look like they came on the leafspring 8.5 housings I've welded them on. Of course one can buy the CNC' ed aftermarket ends... I just like the stealth look of the A-10 ends a little better & a 2.9" OD A10 tapered bearing & seal is a whole lot less expensive than Mosers 3.150" road race tapered bearing. Both can support a very beefy axle & aggressive cornering. Last, if a car is built for great handling, it does not need sealed ball bearing axle bearings, something one needs to consider when custom ordering any performance rearend.