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#1
03-21-2026, 02:50 PM
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65-76 posi diff parts
There's been some chat lately on facebook groups about how some Chevy 12 bolt differential parts will work in the 65-76 B body posi diff, namely the clutch packs for certain. Less certain is the spider gear thrust washers and cross shaft, which may imply spider gears as well. These are all the usually worn out items. Axle side gears are definitely excluded, as Pontiac is 31 spline, Chevy 12 bolt is 30.
It is my understanding the 65-67(or 65-70?) posi diff uses a weaker .750" diameter spider shaft. 71-76 diff use a stronger .875" shaft and corresponding larger spider gears. Can anyone verify the correct date ranges and sizes? As for 12 bolt Chevy, they have a .808" diameter shaft. I have a few mid to late 60 B Pontiac open diffs that have .808" shaft as well, so maybe that is possibility for interchange? Lastly, is there a source for new .875" shaft and thrust washers, and maybe even spider gears?
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Red\black 65 Grand Prix 467 E-head stroker, Viper T-56 6-speed, 4.10 spool |
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