8.2 vs 8.5 10 Bolt Rear
Short answer: All 1967–69 Firebirds used the 8.2″ 10-bolt (a “BOP” Buick-Olds-Pontiac rear) — the size has nothing to do with posi. From ~1970–71 on, Firebirds used the corporate (Chevy) 8.5″ 10-bolt.
Beyond ring-gear size, the 8.2″ uses a weaker cone-type posi that retains at the axle/bearing end, while the 8.5″ uses a clutch-type posi with C-clips inside the carrier (among other differences) — the 8.5″ is the stronger unit.
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Content last modified: June 13, 2026 at 10:06 am
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