Quick performance 9" question

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565bbchevy

Geezer
Aug 8, 2011
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I agree totally, i just might be talking myself out of this. I just wanted to only have to pull a rearend one time was my thinking
Traction is what breaks 7.5" rears, I had a 7.5" with an Auburn carrier and 373 gears behind a healthy 496 BBC in my Monte and I never ran slicks and I also never had traction but it didn't break.
 
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airboatgreg

Comic Book Super Hero
Oct 2, 2016
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The only issue i have is the emergency brake is not what i expected. I went with the rear disc. Still playing with and i will make it work
 

DRIVEN

Geezer
Apr 25, 2009
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*CENSORED*
Do the 9" so I can watch. It'll be my next major Cutlass purchase.
 
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shoedoos

Master Mechanic
Jul 3, 2012
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QP are good people to deal with, each and every question I had, Brydon not only answered in layman terms, but also ventured other options if he thought I had not considered them.....take into account the lower control arm brackets do not have the same angled mounting point for the shock bolt (they didn't make them back when I bought mine), a wedge washer from McMaster Carr will fix that issue though....
 
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Drkuhar

G-Body Guru
Sep 27, 2018
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Girard, IL
QP are good people to deal with, each and every question I had, Brydon not only answered in layman terms, but also ventured other options if he thought I had not considered them.....take into account the lower control arm brackets do not have the same angled mounting point for the shock bolt (they didn't make them back when I bought mine), a wedge washer from McMaster Carr will fix that issue though....
Thanks for the tip. This is the type of information i was looking for. What works and what doesnt.
 

64nailhead

Goat Herder
Dec 1, 2014
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Upstate NY
Save your money is my advice. You don’t need a 9” unless your putting real wood in the stove. Sounds like you’re throwing in some pine lol.
A properly setup 7.5 will withstand 350-400 hp if you don’t run sticky tires and launch it hard. Street (hard) tired that spin easily and a 7.5 will live forever in proper conditions. Of course a 40 year old diff needs ‘proper’ attention.

There are some super cheap upgrades to a 7.5 that will make it live over 450 hp without issue as well.
 
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Drkuhar

G-Body Guru
Sep 27, 2018
507
896
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Girard, IL
Save your money is my advice. You don’t need a 9” unless your putting real wood in the stove. Sounds like you’re throwing in some pine lol.
A properly setup 7.5 will withstand 350-400 hp if you don’t run sticky tires and launch it hard. Street (hard) tired that spin easily and a 7.5 will live forever in proper conditions. Of course a 40 year old diff needs ‘proper’ attention.

There are some super cheap upgrades to a 7.5 that will make it live over 450 hp without issue as well.
I am definitely taking a second thought after seeing some of the post about a 7.5 holding up. I dont run slicks,i mostly run errands, go to a few local car shows and light em up at a stop sign once in a while. Its a large amount of money for no more than i do.
 
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565bbchevy

Geezer
Aug 8, 2011
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Michigan
I am definitely taking a second thought after seeing some of the post about a 7.5 holding up. I dont run slicks,i mostly run errands, go to a few local car shows and light em up at a stop sign once in a while. Its a large amount of money for no more than i do.
Plus if you try to "budget build" the 9" you could be sacrificing strength which is the whole reason to buy one in the first place.
 
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64nailhead

Goat Herder
Dec 1, 2014
5,660
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Upstate NY
I am definitely taking a second thought after seeing some of the post about a 7.5 holding up. I dont run slicks,i mostly run errands, go to a few local car shows and light em up at a stop sign once in a while. Its a large amount of money for no more than i do.

I’ve referenced this in the past, and I’m sure you can find posts identifying this - I have a spare rear in the basement that is a stock factory Torsten diff from a 3rd Gen with 2wd S10 axles - both 28 spline. You have to space the stock brakes 3/16” via a homemade spacer to get the S10 axles to work properly. The rear I described we ran for a year at 500whp (not crank) burnt through multiple sets of tires. All junkyard parts other than the bearing kit. Never ran sticky tires on that rear, but did run 275/40R17’s that were aggressive.

A NA build that makes 400 crank hp will never break that setup. We bought the Torsen off eBay for less than $200 and it was a 3 series that would take 3.08’s and up - we used 3.73’s(from the junkyard of course) ;)
 
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