Seeking 8" Posi Suggestions
3rd Gear Member
Joined: Jan 2007
Posts: 940
From: CT
Stangatic,
Have you seen the aluminum chunks that Currie sells for the 8?
Its called the Alumin8 or something like that. If I had known about those when I rebuilt my rear end, I would have jumped all over it. And I may still get one.
They are something like 30 lbs lighter than the cast iron unit, and stronger too.
Just a thought for your build...
Have you seen the aluminum chunks that Currie sells for the 8?
Its called the Alumin8 or something like that. If I had known about those when I rebuilt my rear end, I would have jumped all over it. And I may still get one.
They are something like 30 lbs lighter than the cast iron unit, and stronger too.
Just a thought for your build...
http://www.currieenterprises.com/ces...E.aspx?id=2435
2nd Gear Member
Joined: Aug 2009
Posts: 476
From: NH
I have a 9" in mine. One thing to remember, anytime you can take one more concern out of the picture makes driving it so much more fun.
Based on the work your putting into this car and for the price difference, I'd say its money well spent for piece of mind. Not to mention, your plans for this car could easily change in the future and it would be nice to "do it right" while your already making a rear end investment. (not that you'd be doing it wrong with an 8", but you know what I mean)
Based on the work your putting into this car and for the price difference, I'd say its money well spent for piece of mind. Not to mention, your plans for this car could easily change in the future and it would be nice to "do it right" while your already making a rear end investment. (not that you'd be doing it wrong with an 8", but you know what I mean)
6th Gear Member
Joined: Apr 2007
Posts: 10,468
From: California
What most people don't realize, is that just swapping a basic 9" in doesn't make the overall rear any stronger. If an 8" will fail by spitting the pinion out the front of the case(which actually takes a fair bit of effort), then a basic 9" that uses the same axles will twist the axles off inside the carrier. You're just exchanging 1 failure point for another.
I'm curious if anyone here has every actually seen a failed 8" rear end. Anyone? Has anyone ever seen a failed 9" rear?
I'm curious if anyone here has every actually seen a failed 8" rear end. Anyone? Has anyone ever seen a failed 9" rear?
6th Gear Member
Joined: Apr 2007
Posts: 10,468
From: California
Stangatic,
Have you seen the aluminum chunks that Currie sells for the 8?
Its called the Alumin8 or something like that. If I had known about those when I rebuilt my rear end, I would have jumped all over it. And I may still get one.
They are something like 30 lbs lighter than the cast iron unit, and stronger too.
Just a thought for your build...
Have you seen the aluminum chunks that Currie sells for the 8?
Its called the Alumin8 or something like that. If I had known about those when I rebuilt my rear end, I would have jumped all over it. And I may still get one.
They are something like 30 lbs lighter than the cast iron unit, and stronger too.
Just a thought for your build...
And it's available with a beefed up pinion support, which is the primary weak point in the 8".
2nd Gear Member
Joined: Nov 2010
Posts: 493
From: Ontario
What most people don't realize, is that just swapping a basic 9" in doesn't make the overall rear any stronger. If an 8" will fail by spitting the pinion out the front of the case(which actually takes a fair bit of effort), then a basic 9" that uses the same axles will twist the axles off inside the carrier. You're just exchanging 1 failure point for another.
I'm curious if anyone here has every actually seen a failed 8" rear end. Anyone? Has anyone ever seen a failed 9" rear?
I'm curious if anyone here has every actually seen a failed 8" rear end. Anyone? Has anyone ever seen a failed 9" rear?
I have broken a couple of 9 inch rears (spider gears and shafts)and have seen a few broken 8 inchers as well...
6th Gear Member
Joined: Apr 2007
Posts: 10,468
From: California
And twisting an axle off can be potentially disastrous. It can destroy the carrier and possibly even the 3rd member, and at the very least throw metal bits into the assembly and ruin the gears and bearings. But if it happens under full power, which it typically does, you risk losing control of the car as the power imbalance at the rear produces insane amounts of torque steer. Wrecking a car over a broken axle is a lot more expensive than just breaking an axle. And even if it is a twisted off axle....how many times and how much money, how often, to keep replacing axles?
There's really no point in going to a 9" unless you go 31spline or larger axles. Otherwise instead of breaking pinion housings, you're breaking axles. But it's still breaking. You can also break spider assemblies in the carrier on either one as well, another weak link.
I've seen a broken 8 here and there, but have seen tons and tons of broken 9" and GM 12" rears. It's more about how it's set up and how it's used, than about what size rear it is. People get so overconfident at the supposed strength of the larger rear ends, that they overlook the reality of what causes failure. People who can break an 8" can break a 9".
A rear end is only as strong as the weakest link. And since 8 and 9" rears use the same axles stock, and axle/carrier failure is common in both....what do you think the weakest link in a standard 8 or 9" rear is? So why go to a 9" that's going to fail at the same point as the 8 will? And if you're at the point where you can spit a pinion out the front of an 8, then you need a 31s+ 9" assembly. But why spend money going to a 9" with the same axles, that won't be any stronger?
And just fyi, a properly built 31s 9" rear end assembly is NOT going to be had for $1,000. $1k for a 9, is a stock posi type 9" carrier with 28s stock axles. A 31s assembly with a heavy duty carrier setup is $2,500 and up.
1st Gear Member
Joined: Apr 2009
Posts: 70
From: Tennessee
in something like a road racing setup with a 500hp 347 and an R compound DOT road race tire
Nasty.
2nd Gear Member
Joined: Nov 2010
Posts: 493
From: Ontario
They used the exact same axles stock. The only difference was axle length, based on the vehicle/housing it went in. 8 and 9 rears share carrier and axle bearings as well. The 8 was just a scaled down 9.
And twisting an axle off can be potentially disastrous. It can destroy the carrier and possibly even the 3rd member, and at the very least throw metal bits into the assembly and ruin the gears and bearings. But if it happens under full power, which it typically does, you risk losing control of the car as the power imbalance at the rear produces insane amounts of torque steer. Wrecking a car over a broken axle is a lot more expensive than just breaking an axle. And even if it is a twisted off axle....how many times and how much money, how often, to keep replacing axles?
There's really no point in going to a 9" unless you go 31spline or larger axles. Otherwise instead of breaking pinion housings, you're breaking axles. But it's still breaking. You can also break spider assemblies in the carrier on either one as well, another weak link.
I've seen a broken 8 here and there, but have seen tons and tons of broken 9" and GM 12" rears. It's more about how it's set up and how it's used, than about what size rear it is. People get so overconfident at the supposed strength of the larger rear ends, that they overlook the reality of what causes failure. People who can break an 8" can break a 9".
A rear end is only as strong as the weakest link. And since 8 and 9" rears use the same axles stock, and axle/carrier failure is common in both....what do you think the weakest link in a standard 8 or 9" rear is? So why go to a 9" that's going to fail at the same point as the 8 will? And if you're at the point where you can spit a pinion out the front of an 8, then you need a 31s+ 9" assembly. But why spend money going to a 9" with the same axles, that won't be any stronger?
And just fyi, a properly built 31s 9" rear end assembly is NOT going to be had for $1,000. $1k for a 9, is a stock posi type 9" carrier with 28s stock axles. A 31s assembly with a heavy duty carrier setup is $2,500 and up.
And twisting an axle off can be potentially disastrous. It can destroy the carrier and possibly even the 3rd member, and at the very least throw metal bits into the assembly and ruin the gears and bearings. But if it happens under full power, which it typically does, you risk losing control of the car as the power imbalance at the rear produces insane amounts of torque steer. Wrecking a car over a broken axle is a lot more expensive than just breaking an axle. And even if it is a twisted off axle....how many times and how much money, how often, to keep replacing axles?
There's really no point in going to a 9" unless you go 31spline or larger axles. Otherwise instead of breaking pinion housings, you're breaking axles. But it's still breaking. You can also break spider assemblies in the carrier on either one as well, another weak link.
I've seen a broken 8 here and there, but have seen tons and tons of broken 9" and GM 12" rears. It's more about how it's set up and how it's used, than about what size rear it is. People get so overconfident at the supposed strength of the larger rear ends, that they overlook the reality of what causes failure. People who can break an 8" can break a 9".
A rear end is only as strong as the weakest link. And since 8 and 9" rears use the same axles stock, and axle/carrier failure is common in both....what do you think the weakest link in a standard 8 or 9" rear is? So why go to a 9" that's going to fail at the same point as the 8 will? And if you're at the point where you can spit a pinion out the front of an 8, then you need a 31s+ 9" assembly. But why spend money going to a 9" with the same axles, that won't be any stronger?
And just fyi, a properly built 31s 9" rear end assembly is NOT going to be had for $1,000. $1k for a 9, is a stock posi type 9" carrier with 28s stock axles. A 31s assembly with a heavy duty carrier setup is $2,500 and up.
Thread Starter
3rd Gear Member
Joined: Sep 2009
Posts: 756
From: Ohio
So I think you all have convinced us to do the 9 inch. Although I know I'll never drive the car hard enough to blow the axles, it is peace of mind and also wouldn't hinder us from any more power in the future if we wanted to beef up the engine. I appreciate all of the input and advice. I agree with 67mustang302 with the fact that it only makes sense to install 31 spline axles if we go with the 9 inch. If we head that direction, which it looks like we are, it will be another $365 or so for new Moser 31 spline axles. The guy is a close family friend who specializes in building rear ends and his highly recommended in our area.
I appreciate the compliments from those who say we can build it ourselves. I don't doubt we can but since we've done everything ourselves so far, I want to put this area in to the hands of a professional.
As far as the gear ratio, do you all think that 3.60 gears would be the way to go? Thanks again.
I appreciate the compliments from those who say we can build it ourselves. I don't doubt we can but since we've done everything ourselves so far, I want to put this area in to the hands of a professional.
As far as the gear ratio, do you all think that 3.60 gears would be the way to go? Thanks again.
