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1958 - 1981 Pontiac Tech & Restoration Firebird - GTO - Fullsize

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Old 04-07-07, 07:29PM   #1
metalhead73
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Default gm 10 bolt, 7.5 or 8'?

I have stock '79 f-bird with a 301. I will be replacing the 301 with a 400. I know my stock rear gears are 2.43 ratio but how can I tell if this is a 7.5 or 8' rear? I need to know this when buying replacement 3.73 gears. Thanks.
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Old 04-08-07, 01:11AM   #2
79bluebird
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it should be a 8.5
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Old 04-08-07, 01:12AM   #3
79bluebird
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my car was a 301 and had a 8.5 rear end
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Old 04-08-07, 01:30AM   #4
Mb125
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take a picture and post it
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Old 04-08-07, 11:43AM   #5
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The stock gear more than likey is a 2.41. To be sure on the front of the right side (passenger side) is a code. Wire brush it and post it here and I'll help break it down for ya.
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Old 04-08-07, 12:24PM   #6
metalhead73
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Thanks guys!
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Old 04-21-15, 05:11AM   #7
rexs73gto
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Your 79 bird has an 8.5 inch rear end & if you have a 2:41 rear gear then when you swap out the gears you'll have to either use a ring gear spacer or get a new center section which is easy to find as any 73-77 A & G body rear end can be used for that or any 73-81 F-body that has at least a 3:08 rear gear can use the center section form that to.
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