8" vs 9"
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Tuned
Joined: Feb 2002
Posts: 441
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From: Vicksburg, MS
8" vs 9"
I keep hearing how the 9" rear is the strongest, and I have been looking for one to fit my application with no luck. I could get a handful of 8" rears with no problem, but I don't know if it would be strong enough. I plan on putting it behind a 400HP 351W. I want to know if there are any specs. out there that give a HP rating on the 8" and 9".
Andy
Andy
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Joined: Jul 2001
Posts: 4,038
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From: South Kitsap County, WA
8" vs 9"
[updated:LAST EDITED ON 04-Apr-02 AT 03:32 PM (EST)]
The 9 inch is not necessarily the strongest of all time. Generally the larger the units ring gear size, the stronger it is. The engineers have to design it to take up more torque (stress and strain)due to the larger size. You should be looking at torque not HP when getting a rear.
The 8 inch was designed for passenger cars with lower horsepower and torque requirements, hence it's smaller ring gear size.
From my personal experience you're going to find more aftermarket kits to strengthen the 9 inch than for the 8. You start with a stronger carrier unit and maintain that by stuffing in the best parts.
The reason people prefer the 9 and say its stronger is because of its reliability. The ease of swapping out center sections, it's the best known, and has all those neat aftermarket parts also contribute to the legend. You also have other manufacturers that used a swapable center section, m*p*r comes to mind.
For your application a BUILT 9 inch would be cheaper in the long run than any boneyard 8 you can get your hands on. There are many webpages/sites on the 'net that should give you a heads up on how much torque/hp a certain rear can handle and the prices it will cost. Keep in mind a nodular iron or billet aluminum carrier will outperform stock castings, but will cost you BIG bucks if done right. A 400 HP 351W will be asking for a nonstock rear if you want to keep smoking the tires or climbing the rocks.
Hope that starts you out in the right direction.
-Kerry
The 9 inch is not necessarily the strongest of all time. Generally the larger the units ring gear size, the stronger it is. The engineers have to design it to take up more torque (stress and strain)due to the larger size. You should be looking at torque not HP when getting a rear.
The 8 inch was designed for passenger cars with lower horsepower and torque requirements, hence it's smaller ring gear size.
From my personal experience you're going to find more aftermarket kits to strengthen the 9 inch than for the 8. You start with a stronger carrier unit and maintain that by stuffing in the best parts.
The reason people prefer the 9 and say its stronger is because of its reliability. The ease of swapping out center sections, it's the best known, and has all those neat aftermarket parts also contribute to the legend. You also have other manufacturers that used a swapable center section, m*p*r comes to mind.
For your application a BUILT 9 inch would be cheaper in the long run than any boneyard 8 you can get your hands on. There are many webpages/sites on the 'net that should give you a heads up on how much torque/hp a certain rear can handle and the prices it will cost. Keep in mind a nodular iron or billet aluminum carrier will outperform stock castings, but will cost you BIG bucks if done right. A 400 HP 351W will be asking for a nonstock rear if you want to keep smoking the tires or climbing the rocks.
Hope that starts you out in the right direction.
-Kerry
