New LS1 Owners - Newbie Tech - Difference between 10 bolt and 9 inch

Hello

I am wondering the differences between the 10 bolt and 9 bolt rear ends. My stock 02 trans am rear is bent so I need a new one someone offered me a 10 bolt but I remembered something like you want to go with a 9". Are they the same thing or are there big differences. I guess I'm just a noob who need some answer.

Thanks
Joe

I'm not an expert because my stock 10 bolt hasn't broke yet but I belive the common issue has to do with the contact area of the ring gear on the pinion gear being much less than a 9" would provide, which allows it to disipate the force across a larger area.. correct me if I'm wrong but that's my theory..

From Brutespeed.com

10 Bolt, 12 Bolt and 9 inch Information

The factory 10 bolt that came in these cars has a very small 7.5" gear. A variation of this rear was used back in the '70's in the Chevy Monza, then in the Chevy S-10. GM had to of known they would have warranty claims when they decided to use this rear in the 3rd and 4th gen f body's, apparently the cost of creating a stronger rear was higher than what they thought the warranty cost would be. This has been a real plus for the aftermarket, as a bone stock LS1 F Body with a manual transmission can break one of these 10 bolt rears! Many people have tried to beef these 10 bolt rears, spending a lot of money in the process. What they normally end up with is a rear that still breaks, as everything on these rears is too small.
The 12 bolt rears that are available for these cars is a step in the right direction. The 12 bolts are well known for being a stout rear that was a factory option back in the day in many performance cars. You can have a 12 bolt in an early Chevelle, Nova, Camaro, etc, and beat the snot out of it and not hurt anything. Put a 12 bolt into a late model f body that uses a torque arm, make a couple 4000 to 5000 rpm launches at the dragstrip, and I can just about guarantee you'll have a lot more gear noise on the way home. The torque arm seems to distort the housing on the 12 bolts, and it seems to happen to all the brands of 12 bolt rears. This does not happen to the 9 inch rears, and there is no price difference between the 12 bolt and nine inch rears. As the horsepower in our engines keep escalating, most people these days go straight to the nine inch rear. The 9-inch has an internal rear-pinion support that also supports the gear end of the pinion to limit gear deflection under high torque loads. This seems to be the major reason why the 9 inch doesn't start whining after high rpm clutch dumps, when the 12 bolt will pick up noise. The 9-inch locates its pinion gear lower on the ring gear to improve tooth contact, better the 12 bolt does. The 9-inch also has a 0.125-inch larger ring-gear diameter and internal pinion support than the 12 bolt.

9"- bigger case, larger gears, lower pinion angle increases contact area.
It is a far superior rear end and when built right can handle a ton of power.

Big upgrade.

I run a Moser 9". It's bigger, heavier, kills a few mph, but in turn it's stronger, takes any abuse I throw at it, better posi choices, traction is better with rear end set up etc.

Bob @ Brutespeed is the one to talk with on this.

I bought mine through him.

Its different , they are about same as cobalt SS is to a CTS-V

^ wtf??? that's a horrible comparison.

one is weak and shitty.......the other rules and is awesome


there is some horsepower loss through the bigger 9'' rear, but reliability far outweighs that loss

gear swap in the 9 are a breeze.

the 9's have a third member that absorbs most of the shock of launches causing it to whine less than any other rear end


the 10 bolts are not even trustworthy on stock cars. they whine...leak from pinion seals, and sell for around 100-300 dollars depending on what shape they are in when taken out. if they would have put a 9 in to start with and a 4l80.....that would have made the car bullet proof at 400rwhp or more.

10 bolt is stock junk, 9" is an excellent aftermarket rear. Thing to not forget though is your talking about like a $2000 difference between the prices of them... so keep that in mind. Outside of price there is no reason to go with a 10 bolt though. I am in the process of buying a rear right now... though I actually went with an S60.

The stock 7.5 10 bolt cannot even be compared to a 9 inch in strength. The 9 inch has an extra pinion support bearing at the end of the pinion gear which doesn't allow deflection under load like a 10 bolt or even a 12 bolt rear end. Also as mentioned above, the pinion gear is placed in a much better position in the 9 inch to allow more teeth to be in contact with the ring gear. The nine inch also has a dropout style third member which allows the axle housing to remain in the vehicle. This allows you to make ring and pinion changes without disassembling the entire rear suspension of the car. That being said it is very cost prohibitive for most of us including myself so I'm running the little 10 bolt hard until it finally breaks then ill worry about replacing it.

you mite find a used 9" in the used parts section .check the rear end section for more info and choices.you can find used gm 10 bolts for $100.