1980 Firebird 10bolt posi rearend - Hot Rod Forum : Hotrodders Bulletin Board
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Old 11-22-2004, 07:57 PM
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1980 Firebird 10bolt posi rearend

I am considering on buying a 1980 Firebird 10 bolt posi rearend with 256 gears for my 53 Chevy pickup but i want to make sure it is what they say it is.Is there ID numbers to tell me for sure and how easy is it to find 308 gears for it??

thx in advance

Greywulf

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Old 11-22-2004, 09:24 PM
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I would pull the cover to verify the gear count and posi
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Old 11-22-2004, 11:12 PM
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A 1980 Firebird would have an 8.5" rear end. The posi carrier from a 2.56 geared unit will not work with 3.08 gears. The 2.56 uses a 2-series posi carrier (cast 410409N), while the 3.08 needs the 3-series carrier (cast 410408N). In an 8.5, the 2.73 gears also use the 3-series carrier.

Gear tooth counts are often marked on the edge of the ring gear, usually right next to a date code. If you see four numbers right close to each other, for example 41 16 12 79, two will be tooth counts, & the other two will be month & year of manufacture. Divide the ring gear count (usually between 35 & 45) by the number next to it to get the gear ratio (41 divided by 16 = 2.56).
12 79 would mean made in December of 1979.

Novas from the early '70s (starting in '72) with 3.08's were fairly common, but their rear ends are a little narrower than the '70-'81 Camaro/Firebird's.
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Old 11-23-2004, 06:47 AM
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All of the ring and pinion manufacturers sell gears that would normally need a different carrier for that ratio.
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Old 11-23-2004, 03:40 PM
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Thx all for your help....I guess that it isn't worth buying then if i can't change gears in it without buying another carrier
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Old 11-27-2004, 01:25 PM
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aren't those 3rd gen f-body rearends weak, too?
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Old 11-27-2004, 01:50 PM
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3rd gen f-bodies are 83+, 2nd gen use the 8.5" in most cases that is quite strong
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