how to tell if you got a 7.5 or 7.65 10-bolt
11-30-2008, 01:13 PM
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Car: 1988 Firebird Formula WS6
Engine: LO3 305 tbi
Transmission: 700 R4
Axle/Gears: 3gen housing zexel torsen posi 3.42
how to tell if you got a 7.5 or 7.65 10-bolt
I have a 88firebird formula ws6 with a 305tbi/700R4/ and i know its a 10-bolt open diff. I want to beef it up but I need to know if its a 7.5in or 7.65in
11-30-2008, 01:26 PM
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Car: 86 Trans Am, 92 Firebird
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Axle/Gears: Moser 9", 3:70 trutac, 3:23 torsion
Re: how to tell if you got a 7.5 or 7.65 10-bolt
if its the original rear its probably a 7.625, but that number means nothing for most upgrades.
it only matters if you are swapping the innards of the carrier, because the spacing inside, where the spiders gears/posi unit go, it different by about a quarter inch.
But nobody does that, they just swap out the entire carrier. Unless you are buying a powertrax locker.
it only matters if you are swapping the innards of the carrier, because the spacing inside, where the spiders gears/posi unit go, it different by about a quarter inch.
But nobody does that, they just swap out the entire carrier. Unless you are buying a powertrax locker.
11-30-2008, 01:40 PM
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Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
Re: how to tell if you got a 7.5 or 7.65 10-bolt
Around 1986, GM upgraded to 7-5/8". Nothing else is different, just the size of the ring gear was increased. 7-1/2 and 7-5/8 components are the same.
Even though the ring gear is 7-5/8, the diff is still called a 7-1/2".
Yours will have 26 spline axles unless a previous owner upgraded to 28 spline.
Even though the ring gear is 7-5/8, the diff is still called a 7-1/2".
Yours will have 26 spline axles unless a previous owner upgraded to 28 spline.
11-30-2008, 01:43 PM
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Car: 1988 Firebird Formula WS6
Engine: LO3 305 tbi
Transmission: 700 R4
Axle/Gears: 3gen housing zexel torsen posi 3.42
Re: how to tell if you got a 7.5 or 7.65 10-bolt
if its the original rear its probably a 7.625, but that number means nothing for most upgrades.
it only matters if you are swapping the innards of the carrier, because the spacing inside, where the spiders gears/posi unit go, it different by about a quarter inch.
But nobody does that, they just swap out the entire carrier. Unless you are buying a powertrax locker.
it only matters if you are swapping the innards of the carrier, because the spacing inside, where the spiders gears/posi unit go, it different by about a quarter inch.
But nobody does that, they just swap out the entire carrier. Unless you are buying a powertrax locker.
----------
Around 1986, GM upgraded to 7-5/8". Nothing else is different, just the size of the ring gear was increased. 7-1/2 and 7-5/8 components are the same.
Even though the ring gear is 7-5/8, the diff is still called a 7-1/2".
Yours will have 26 spline axles unless a previous owner upgraded to 28 spline.
Even though the ring gear is 7-5/8, the diff is still called a 7-1/2".
Yours will have 26 spline axles unless a previous owner upgraded to 28 spline.
Last edited by FireTurdWS626; 11-30-2008 at 01:44 PM. Reason: Automerged Doublepost
11-30-2008, 02:32 PM
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Car: 88 Formula 350
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Axle/Gears: 9" 3.89
Re: how to tell if you got a 7.5 or 7.65 10-bolt
Yes either carrier size will work, but you will need a 26 Spline as a must.
11-30-2008, 02:36 PM
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Car: 1988 Firebird Formula WS6
Engine: LO3 305 tbi
Transmission: 700 R4
Axle/Gears: 3gen housing zexel torsen posi 3.42
11-30-2008, 02:38 PM
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11-30-2008, 04:30 PM
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Re: how to tell if you got a 7.5 or 7.65 10-bolt
You'll need 28 spline axles specific to a third gen. 90-92 third gens got 28 spline axles but any aftermarket ones for 82-92 will work. There are no other factory 28 spline axles which will be the proper length.
11-30-2008, 11:41 PM
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Car: 1988 Firebird Formula WS6
Engine: LO3 305 tbi
Transmission: 700 R4
Axle/Gears: 3gen housing zexel torsen posi 3.42
Re: how to tell if you got a 7.5 or 7.65 10-bolt
alright guys i think i soaked it all in thanx for all the help
01-13-2009, 12:40 AM
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Car: 1982 Camaro Z28 w/ RS groundfx
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Transmission: Tranzparts 700r4
Axle/Gears: 3.23's
Re: how to tell if you got a 7.5 or 7.65 10-bolt
So, if you have a 7.5 rear you can go ahead and purchase a carrier meant for the 7.625 and use said 28 spline axles? Seeing that summit doesn't offer a 28 spline carrier for the 7.5... Sorry for my noobness, but just started looking into this.
01-13-2009, 12:44 AM
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Re: how to tell if you got a 7.5 or 7.65 10-bolt
The carriers, and absolutely everything else except the gears themselves are exactly the same. For all intents and purposes, the 7.5 and 7.625 are one and the same.
01-13-2009, 08:19 PM
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Car: 1988 Firebird Formula WS6
Engine: LO3 305 tbi
Transmission: 700 R4
Axle/Gears: 3gen housing zexel torsen posi 3.42
Re: how to tell if you got a 7.5 or 7.65 10-bolt
Just a heads up for my rearend build i ended up using axles from Yukon, a eaton posi unit, and richmond gear set (3:27) and finished it off with a TA performance cover w girdle. while i had the axels out i upgraded the rear brakes with a package from hawksthirdgenparts.com
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