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View Poll Results: will it hold
will it hold 2 40.00%
will it brake after 3-5passes 3 60.00%
Voters: 5. You may not vote on this poll

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Old 02-24-2008, 04:24 PM
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rear end strength

Ok guys and girls here is the deal.

I have a 86 Z-28 and the engine just took a dump on me I'm pretty sure it spun a rod barring so the block is gone. I'm planing on putting in a 350 rated at 400hp with a 350 turbo trans and a 3000 stall converter and I'm going to back it with a 7.5 10 bolt rear end. now the question is how strong can I make this little rear end? I am putting new 28 spline's in it with a new posi traction unit out of a 95 camaro, with 3.73 gears and c-clip elm's. I have heard from a few well know camaro people I know that the rear is rated a 400hp from the factroy and the person I am having build it has a camaro just like mine with a 521 RWHP 383 backed by a 7.5 rear. I am not going to use slicks on it so I don't twist the housing and I really don't have the money to get a 12 bolt or a 9 inc, but I really want to get into the racing sceen out here cuz in decature the money is easy and 11's are decent so can you all please help me? thank you.

Trey

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Old 02-24-2008, 05:52 PM
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Should hold....but you may not like it. A narrowed 9" or a 12 bolt may be a better choice.
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Old 02-24-2008, 06:04 PM
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thanks man. I want to go with a 12 bolt wonce I make some money of the car.
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Old 02-24-2008, 06:19 PM
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why don't you use the rear out of the 95 or are they the same thing cause them are pretty good rears
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Old 02-25-2008, 10:03 AM
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Quote:
Originally Posted by camaro86
Ok guys and girls here is the deal.

I have a 86 Z-28 and the engine just took a dump on me I'm pretty sure it spun a rod barring so the block is gone. I'm planing on putting in a 350 rated at 400hp with a 350 turbo trans and a 3000 stall converter and I'm going to back it with a 7.5 10 bolt rear end. now the question is how strong can I make this little rear end? I am putting new 28 spline's in it with a new posi traction unit out of a 95 camaro, with 3.73 gears and c-clip elm's. I have heard from a few well know camaro people I know that the rear is rated a 400hp from the factroy and the person I am having build it has a camaro just like mine with a 521 RWHP 383 backed by a 7.5 rear. I am not going to use slicks on it so I don't twist the housing and I really don't have the money to get a 12 bolt or a 9 inc, but I really want to get into the racing sceen out here cuz in decature the money is easy and 11's are decent so can you all please help me? thank you.

Trey

In two words; hell no. The 7.5 is not up to 400 hp, let alone the torque that will accompany it. If you plan on even vaguely sticky tires, kiss it goodbye soon.

I also suggest against using the 95 axle. It is the same 7.5/7.625 axle, but its wider than your 86. So not only do you not get any more strength, you're going to have to custom fit an axle to your car.

My buddy put a 350- hp LS1 in his 85 F-body and the rear axle died within a month. He pulled it out, had it rebuilt with new bearings, seals, ring and pinion, stud girdle in a cast cover, and 28-spline carrier with upgraded axles. Within 6 months it died... and not just died, grenaded. It ripped a hole in the rear floor pan, destroyed the rear bumper, and made scrap iron out of the axle housing. The passenger side axle came out of the housing and made mincemeat of an FBI agent's Crown Vic windshield in the next lane.

The 7.5 can be made to handle the same torque as a stock 8.5, but why spend thousands getting it to handle as much torque as a stock 8.5 when you could spend it on getting a 12-bolt or 9" that will take absolute abuse? Upgrade. You'll sleep better at night.

You need a third option on your poll: "will it pee its pants and melt from fear when you fire up the engine."
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Old 02-25-2008, 10:13 AM
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Hi Trey,
Listen to Curtis, He knows what he's talking about.
Good luck,
Rich
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Old 02-25-2008, 10:46 AM
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RE:rearend strength

Hi first of all how are you going to make any money at racing if you still sitting at the starting line? your going to lose if you use that rearend! l have a s-10(big block) and l cheaped out twice with the rearend, the first rearend that came in it worked until l played with it, the very first time, and bang call a towtruck, then second time had a spool in it, new harden axle (bal bal) and l took it easy until the one day l need it and then the both axles snapped and then towtruck again, so in the end l spend well over $1000 and got nothing then l spent more to get the rearend that would work and it was cheaper than messing with the other ones, so over built don't under built, l do know guys running s-10 rearends in s-10's with 305 or 350's but there only stock motors with no traction and no weight, l learn my lesson you will to if you do it!!!! oh and its no fun a 50 mph trying to hold on to it when it goes, isn't your life worth more??????? TROY
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Old 02-25-2008, 11:17 AM
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Dana 60 gets my vote. I have broken many a 12 bolt rear end.
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Old 02-25-2008, 07:17 PM
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My friend had a 84 Regal with a 355 with a TH350 and 7.5 10 bolt. When we dynoed it, it was at 367 HP and 392 FT. LBS. Needless to say, he broke an axle, which he replaced and then the ring gear he had on (Richmond) exploded. Not just broke a tooth, but literally exploded. I would definitely upgrade to 8.5 10 bolt or 12 bolt. When i was lookin around for a rear for my Monte, i found a bunch of Camaro rears (12 bolts) around my area that were adapted to your car.
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Old 02-25-2008, 10:36 PM
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I'll be sending 425 hp from a 383 LT1 and 6-speed manual to my 8.5" rear and I won't worry a second about it... even with 315mm sticky rubber. I probably could break it if I tried, but I doubt i'll ever break it. I know many Impala SS guys dragging 4000-lb cars into the 11s on the 8.5 with slicks and lifting a front tire. I don't recommend that much, but its a pretty stout thing if set up right.

12 bolts are good bit stronger, 9" and Dana 60 are super strong, but both VERY heavy.
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Old 02-28-2008, 01:35 AM
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Rearend.

Sorry, But anything with any serious horsepower and more Importantly Torque, I would not use a GM rear assembly. Spend the extra and Get a 9" Ford with at least 31 spline axles. The GM rear axle assemblies are simply not worth the money spent to get them strong enough to live up to the 9" Ford. Don't get me Wrong, Im a Chevy Guy, but the axle is where GM failed to build it better! A lot of My friends have Suburbans for family vehicles and every single one has had a rear differential failure. That ought to tell you something. I am also not fond of the GM "C"-Clip axle retention design. This design can cause the axle to come out of the housing in the event of a axle failure. NHRA requires axle retention plates installed if using a GM type rear in a fast car. That should also be a warning about the GM rearends. Just My opinion, Good luck on your project!
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Old 02-28-2008, 07:05 AM
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From faded memories of a long, long time ago, strongest first:

Dana 60
Ford 9"
Chevy 12 bolt
Chrysler 8-3/4"
57 - 64 Olds/Pontiac

The 9" is so much lighter than the 60, it became the rear of choice. With all of the aftermarket attention, it may have equaled or exceeded the 60 in strength. The 12 bolt should have the c-clips eliminated.
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Old 02-28-2008, 12:22 PM
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Quote:
Originally Posted by redsdad
From faded memories of a long, long time ago, strongest first:

Dana 60
Ford 9"
Chevy 12 bolt
Chrysler 8-3/4"
57 - 64 Olds/Pontiac

The 9" is so much lighter than the 60, it became the rear of choice. With all of the aftermarket attention, it may have equaled or exceeded the 60 in strength. The 12 bolt should have the c-clips eliminated.
I can get behind that list. I'd throw in that the Ford 8.8 is a corporate copy of the GM 12-bolt so its a viable option. The problem for 3rd gen F-bodies is the torque arm suspension. You're kinda at the mercy of the aftermarket and what they make to fit the torque arm. For the most part, that means 12-bolt or 9"
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Old 02-28-2008, 01:13 PM
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Help me understand. I'm fairly mechanically inclined, but is an 8.5" 10 bolt as strong as an 8.5" 12 bolt?(Prolly not, but close?) Don't the number of bolts refer to the bolts holding the ring gear in? And what about the number of bolts in the back of the housing holding the cover on? Doesn't that just tell you that one housing is a little bigger than the other? As I understand it you can get an 8.5 in the 10 bolt housing and in the 12 bolt housing. An 8.5" ring gear is stronger than a 7.5" or an 8.2" because the load is applied farther away from the center. As I see it, with a larger housing you could get larger bearings. This would make for longer life. Am I close to knowing anything about what I'm talking about?
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Old 02-28-2008, 02:34 PM
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8.875" 12-bolts are about the same strength as the newer (~88-up) 8.5"/8.6" 10-bolts. They both have the same size pinion shaft and 30-spline axles. Truck 12-bolts have a smaller pinion. For the most part a larger ring gear means it will stand up to more torque. There are also a few other things to factor in like gear face width and hypoid distance.

On GM/AAM axles the number of bolts stands for the number of bolts that hold the cover on. In some cases the ring gear is also held on with the same number of bolts. A 10-bolt has 10 ring gear bolts and a 12-bolt has 12. However all 3 14-bolts have 12 bolts holding the ring gear on AFAIK.
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