Why a 9" over a 12 bolt?
 

Why does everyone seem to want to buy a new 9" for their GM cars when you can purchase a new 12 bolt? Unless you are looking to change gearsets in a hurry, a 12 bolt will hold up fine for what the majority of people will be using their Pro-touring cars for. Do people feel the 12 bolt will not hold up or do they actually like the appearence of a 9" under their GM car. I AM NOT KNOCKING FORD IN ANY WAY SHAPE OR FORM!! I want to make that clear, I like all American muscle cars wether they are GM ,FORD or CHRYSLER. I would like to hear what people think. Most peolple I know choose to stay with a 12 bolt in their GM car. When I look at all these awsome cars I notice a lot of people choose a 9" and always wonder why. Thanks

its preference I guess......one benefit that comes to find is no c clips or c clip eliminators on a 9in. THe gear sets are bigger and stronger. No cover on the rear allows the use of a rear axle back brace. Im sure there are more but its early and i can't think right now. :_paranoid

When buying new
 

Most of these guys seem to be buying new. You can buy a new 12 bolt from Moser with ford housing ends. You now have no c-clips. Check out www.rhodescustomauto.com and check out the two camaros on the home page, 1 red and the other blue. Both run 12 bolts without a problem. If you want to see more of the car go to finished cars and you will see more photos of the car. And they look better. I have been friends with Ron (red Camaro) since we were kids. That 12 bolt has been in his car forever. Can anyone agree that a 12 bolt looks perfect under a camaro instead of a 9 inch, or I am just being a bit anal about it? Speaking of Rhodes Custom Auto. If anyone needs any work and lives near Delware, Ron and his father Larry do incredible work. They have been building street rods, custom street cars and race cars for 30 plus years. They build a lot of show cars also. Starting to sound like an advertisement so I will end it now. Thanks Dave

I have been wondering same too. Does GM rear have pinion in more favorable postion than 9" ? Steve reported at he had some wheel hop with 9" but not with 12 bolt?

What about the weight differences?

yes you can custom order the rear end with 9in ends. A 12 bolt takes less power to turn but they will not hold as much power as a 9 in due to where the pinion rides on the ring gear I think...I am not a rear end guru though.

the 9" has an extra bearing/support on the snout of the pinion, making for a stronger interface between the ring & Pinion, and a larger diameter ring gear. more aftermarket parts BY FAR, easily weldable formed plate steel center section, opposed to the cast center of a 12 bolt. easy gear changes, cheaper LSD's, etc. blow up a 9" third on a road trip, slap another one in from a junkyard, blow up a 12 bolt on a road trip, find a new rear. :unibrow:

9 inch
 

Yes 9 inch rears have many advantages when it comes to the things that have been referred to. Who uses their pro touring car in such a manner that the likleyhood of blowing it up is really there? Are these pro touring cars yanking the wheels of the ground in 1/4 mile drag racing? Check out www.rhodescustomauto.com and that camaro has a 1.3 60' time with a 12 bolt. Does anyone with their street cars stress their rears more than that? If your car blows the rear on a road trip who is actually going to do the that kind of work on the side of the road or in a parking lot? I don't know anyone who would. It would be trailered back home no matter what kind of rear blew up. Besides, how many people with 9" rears in their street car actually have a spare center section already set up and ready to install in the event a rear blows up on a road trip.

sounds like you have your mind made up.

Well, since we have been selling the crap out of Moser rears, I have learned a bit about rear ends. The hot set up in a differential today is the True Trac. Actually, a 12 bolt Moser 33 spline True Trac is stronger then a 9" True Trac partly because it is bigger then the 31 spline offered in the Ford, and also because Moser has built up the original 12 bolt with their new castings. The other weakness in a 12 bolt is that the pinion tries to push the center chunk out of the back of the rear. A Performance cover takes care of this buy adding support to the center chunk main caps, which I have proven with 900+ HP in my street racer launching 100s of times on slicks with 1.30 short times. Now if True Track would make a 35 spline for the Ford like they do for the Dana / Moser 60s, that might turn things a bit.

So for GM guys I sell mostly 12 bolts with True trac's and with "Torino" (Ford Big Ends) and a performance support cover. If someone has a LOT of power, they are forced into a 35 spline Detroit Locker. Which if you ever had a Locker on the street, it is like driving a spool. UGH!

me. i have a spare 9" third that will go with the car on long trips, along with the tools needed for a change, as soon as the car runs, im driving down to arizona, from WA, hittin vegas on the way down :captain: