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Old 08-14-2008, 12:48 PM
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cutlass rear end

hey guys, i'm really inexpierienced with rear end stuff, never really messed with it before. How do i tell the 7.5 and 8.5" apart? Is it just something i can measure or does anyone have any photos, my car is an 82 cutlass supreme, but i got it from a junk yard for $75 and it already had a lot of stuff changed on it. How do i know what i have, and what is the best way to keep her from doin the "One wheel peel", It's gonna be a street/strip car. i thought about a mini spool, but i've heard bad things for the street. thanks

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Old 08-14-2008, 01:01 PM
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hmmm

if i am not mistaken it is the same rearend as the 70's camaro which is an 8.5 but i am not 100% you'll just need to measure the ring gear ans no spool on the street trust me go with a locker
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Old 08-14-2008, 03:14 PM
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Unless someone swapped it it is a 7.5 open diff. 7.5's have two peaks on the side/bottoms. 8.5 I believe have them in the same place, but are more squared off.

8.5 is g-bodies only came in GN's and maybe H/O's.
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Old 08-14-2008, 03:47 PM
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Quote:
Originally Posted by BMM
Unless someone swapped it it is a 7.5 open diff. 7.5's have two peaks on the side/bottoms. 8.5 I believe have them in the same place, but are more squared off.

8.5 is g-bodies only came in GN's and maybe H/O's.
Actually, the 84 H/O and the 85-87 442s all came with 8.5" axles with 3.73 gears. The 85-87 GNs came with 8.5" axles with 3.42 gears.
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Old 08-14-2008, 06:42 PM
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7.5" or 8.2" or 8.5" Rear ID>
http://www.buickperformance.com/85rear.htm

http://dyeager535.topcities.com/diffid.html

http://www.oldsmobility.com/10bolt-tech.htm
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Old 08-15-2008, 07:47 AM
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posi

thanks for the info guys, especially the pics helped a lot. I'm pretty sure i do have the 7.5" 10 bolt. I think it has 3.08, or 3.23 gears in it, but a gain, im not sure and dont know how to tell. My car was the more sporty edition w/ the factory spoiler, 307, ect. My questions are how can i tell what gears are in it, and what other vehicle's are there that would have a 7.5" rearend w/ a posi in them. I'm lookin to snag one from a junk yard if possible.
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Old 08-15-2008, 09:00 AM
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The GN/GrandNational & HO/HurstOlds 8.5" rears are hard to find but are much better than the weak 7.5". A lot of the G-Body owners are using the Mustang 8.8" rears, the upper control arm mounts work if you use the adjustable Mustang arms. The lower control arm mounts & spring seats will have to be swapped from your 7.5" rear. This link did have Pics but they're gone, may be able to ask for them tho'.
http://gbodyforum.com/viewtopic.php?p=17067#17067

http://www.cheperformance.com/cartge...st.asp?scat=71
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Old 08-15-2008, 09:51 AM
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locker

ok, i read the thread that a guy posted on here about a ss monte rear end, and i think it was you (ssedan) that showed him a link to a detroit locker for the 7.5". Like i said i have NO expeiriend with rearends, so my question is, how exectly does a locker work vs. a posi, and limited slip. Is a locker ok for street use? my motor is a SBC 355 around 375-400 HP/ TH400 trans. will my stock axle splines hold up to the job
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Old 08-15-2008, 10:10 AM
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Quote:
Originally Posted by eatonde
ok, i read the thread that a guy posted on here about a ss monte rear end, and i think it was you (ssedan) that showed him a link to a detroit locker for the 7.5". Like i said i have NO expeiriend with rearends, so my question is, how exectly does a locker work vs. a posi, and limited slip. Is a locker ok for street use? my motor is a SBC 355 around 375-400 HP/ TH400 trans. will my stock axle splines hold up to the job
Most prefer clutch or gear type posi's on the street. Lockers & especially spools are more suited for off road. There are air and electric type lockers which operate as a regular open diff unless manually locked and are very good for the street. I would suggest upgrading your axles if you plan on any strip use with sticky tires or slicks. Here's some Diff Info. and look at the top of page on this forum in the Knowledge Base & Wiki Articles for Diff Info>
http://www.classicfirebird.com/hand/build13.html

http://www.howstuffworks.com/differential.htm
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Old 08-15-2008, 12:52 PM
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Quote:
Originally Posted by mcharger440
if i am not mistaken it is the same rearend as the 70's camaro which is an 8.5 but i am not 100% you'll just need to measure the ring gear ans no spool on the street trust me go with a locker

8.5 inch rears were first used in '71. If you see a 10 bolt under a 70 its likely an 8.2 or a swapped in 8.5 from a nova or some such.

K
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Old 08-15-2008, 05:54 PM
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Quote:
Originally Posted by mcharger440
if i am not mistaken it is the same rearend as the 70's camaro which is an 8.5 but i am not 100% you'll just need to measure the ring gear ans no spool on the street trust me go with a locker
What, the G-body? Not even close. First, the 70-81 Camaro is leaf spring, the G-body is coil spring. Second, the G-body cars as noted use the 7.5" axle except for the 442/GNs. The THIRD GEN F-body cars used the 7.5" axle, but again the housing is different. The internals will swap, as will those from an S-10.
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Old 08-15-2008, 08:07 PM
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Also keep in mind that the 7.5 from 78-80 or 81 (forgot the year of change) are 26 spline axles and 81 and on are 28 spline.
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Old 09-01-2008, 10:45 PM
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s 10 gears

you said the internals from an s-10 will swap out? do you know what gear i would (most likely) see in an s-10 at a junk yard? Is the S-10 Blazer included in this. Is the S-10 a Posi or open style diff like mine, I'm really lookin at going with a regular posi now, cuz it is gonna be mostly a street car. Any info on this or what would be good to steal the inerds from at a J/Y would be a big help and really same me some money. Thanks guys
Danny
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