8.5 in rearend

g0thiac

G-Body Guru
Sep 6, 2020
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582
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A Holiday 88 would be a B body. Not the same rear.
I know that, but someone had brought up the B Body, thats why I am asking.

So again, I am asking what are my options for spinning both tires 🙃🤣🤣🤣
 

doood

Amateur Mechanic
Sep 24, 2020
492
661
93
What year is it? Pre 88 are 28 spline axles. 88-up are 30 spline.
Stay away from the junk Gov Locks out of trucks.
I haven't assessed this 8.5" I bought today yet, but I'll likely buy a kit from quick performance for posi and axels. If I reuse nothing but the housing, If I can go to 30 spline, might do that. Maybe trutrack if price is within a $100 of clutch posi. I wonder If the '75 Seville disk kit from inline tube will fit, since I got no brakes to start with.
 

gnvair

Royal Smart Person
Sep 1, 2018
1,089
1,284
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Southern New Jersey near Philly
I haven't assessed this 8.5" I bought today yet, but I'll likely buy a kit from quick performance for posi and axels. If I reuse nothing but the housing, If I can go to 30 spline, might do that. Maybe trutrack if price is within a $100 of clutch posi. I wonder If the '75 Seville disk kit from inline tube will fit, since I got no brakes to start with.
Not sure what size wheels you have but I'd do 98-04 Blazer or the 98-02 F body rear discs before using old iron caliper set ups. You need 16" or large wheels for the F body discs
 
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doood

Amateur Mechanic
Sep 24, 2020
492
661
93
Not sure what size wheels you have but I'd do 98-04 Blazer or the 98-02 F body rear discs before using old iron caliper set ups. You need 16" or large wheels for the F body discs
I have the blazer disks up front, so I should do the blazer disks in the back and change the proportioning valve and change the master cylinder too. Just make it all blazer, right? I have 17" wheels.
 

vanrah

G-Body Guru
Apr 16, 2013
879
1,189
93
Near Afton, Wisconsin
Greetings guys; Nice write up fellas, very informative. This 8.5 was from a Buick open (?) 3.43. I had replaced ALL the internals & had some gussets welded on tying the tubes & mounting points together for additional strength. Ole' Bob.
 

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565bbchevy

Geezer
Aug 8, 2011
9,559
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Michigan
I haven't assessed this 8.5" I bought today yet, but I'll likely buy a kit from quick performance for posi and axels. If I reuse nothing but the housing, If I can go to 30 spline, might do that. Maybe trutrack if price is within a $100 of clutch posi. I wonder If the '75 Seville disk kit from inline tube will fit, since I got no brakes to start with.
I know you stated you didn't want a 9" in your car because it's a Ford even though in the long run it would have cost less, but if you only end up using the crusty 8.5 housing with unknown history that cost $1300 plus I assume fuel and 7 hours of your time wouldn't it have been a better option just to put that towards a new bolt in 12 bolt to keep it GM and be stronger? Obviously it's more money but it's new and has never been abused or even had rust on it.
 
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doood

Amateur Mechanic
Sep 24, 2020
492
661
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I know you stated you didn't want a 9" in your car because it's a Ford even though in the long run it would have cost less, but if you only end up using the crusty 8.5 housing with unknown history that cost $1300 plus I assume fuel and 7 hours of your time wouldn't it have been a better option just to put that towards a new bolt in 12 bolt to keep it GM and be stronger? Obviously it's more money but it's new and has never been abused or even had rust on it.
Your argument is solid, though I think rust on a casting this thick is no big deal. I believe the spring perches are solid enough to use as is, although the corrosion has reduced their thickness noticeably. I'll get a couple opinions on that and maybe have new ones welded on.

$300 Axels
$600 QP posi and bearings kit
$20 Rattle can black
$100 seals, gear oil, etc.
$300 tools

That's $2600.

If I need help, add $500 labor.

That's $3100.

I've seen a bolt-in 12-bolt for $3300 no brakes on clearance from a shop in Ohio (attached). Customer didn't take receipt. No brakes.

I'll probably spend $500 on brakes and hose.

So, it IS pretty close to a wash, but my decision was based on belief I would spend $4k on new 12-bolt. I think the 8.5" will be rebuilt and installed for $3000.

I've been looking in to this for a while. I don't have buyer's remorse (yet). It'll work out.
 

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g0thiac

G-Body Guru
Sep 6, 2020
939
582
93
What year is it? Pre 88 are 28 spline axles. 88-up are 30 spline.
Stay away from the junk Gov Locks out of trucks.
Oh it is out of a Olds from '79, but yeah I agree there lol 🤣🤘
 

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