MONTE CARLO How does a 7.5 rear end die?

Sep 22, 2023
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I've heard that with the 10 bolts rear ends the axles will walk out and destroy your car with them. I was wondering if this is true for the 7.5 as well.

I'm current building a 84 monte carlo ss that's gonna have around 450ish crank hp with a 350 sbc. And I want to know if just sending the rear end without replacement is just a totally bad idea. If it's gonna explode and take me and the car with it I'm definitely gonna look into a new rear end.
 

abbey castro

Royal Smart Person
Oct 31, 2015
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Any axle held in place by "C" clips inside the differential has the potential to break and let the axle walk out of the axle tube with the tire damaging the fender. That is why in certain classes only axles held in place by backing plate w/bearings are mandatory. I never seen a "C" clip let the axle walk out, I've seen broken axles and differentials grenade! I think you'll grenade it sooner or later with sticky tires. It will last for awhile but at any moment "boom" I'm running a Strange S60 (Dana60) .
 

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pagrunt

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Sep 14, 2014
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Personal experiance it's in a glorious surpising boom that may even give the feeling of a wheel hop. This was with a 305 inching towards 200 horses with a 4 speed manual behind it. This was from the spider gears & guts calling it quits from too many clutch dumps. Parts are also softer than they should be so too much stress on them isn't good. Money cam be put into the 7.5 to make it stronger but depending on your planned use for the car when you're done bulding it will determin if this route or go aftermarket.
 
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SoFloG

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Mar 9, 2016
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In my experience the G80 gov lock posi failed then little crunchy ticking type sounds appeared after doing some burnouts. I've seen other 7.5/8.5a on the street just fail and just not fucntion. I don't think you have to worry about it exploding dangerously or the axles ejecting unless you're at the track on slicks with a lot of power and or have huge rims.
 
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Oct 14, 2008
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The spider gears are soft, they explode, mine did. The Monte SS 7 5/8" spider gears are more evenly sized and should hold up better. The 26 spline axles and C clips are weak points. Not all 8.5" GM rears had C clips, Olds have bolt in axles through the mid 70's.
 
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DonF

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Nov 1, 2015
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If you want to stay on the cheaper side and not spend a couple grand on a 9 inch or 8.5 just put in a quality center chunk. I run an Auburn posi and 3.42 gears, diff cover with bearing cap support, stock axles, and fat tires that slip just enough to not break sh*t.... and that behind a 500+hp big block
 
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Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
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The big problem with 7.5s are the small pinion gears. The higher the ratio the smaller and weaker the pinion is.

338632d1501315854-best-relative-10-bolt-dsc_1028ccrccaawtwts.jpg
 
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bracketchev1221

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Like was said, it won't come out of the housing. But its not going to live long if it really is as much HP as you say. Just don't plan on ever trying to get any traction with it. Like was also said tire spin will be your friend. the sudden load is what will break the axles.
 
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