I only have about 400 hp so I know both would be strong enough. I have a line on a brand new Currie 9" for Third gen for a great deal but had my heart set on a 12 bolt. Is there any reason I shouldnt go with the 9"? Looking for opinions. Thanks.

 

If it is a direct bolt-in it would be hard to beat. You could have more than one pumpkin set up so you could run low gears to drag race, higher gears for the street and even higher gears for your record run at the Bonneville Salt Flats . Just kidding. Gear changes are much easier on the 9inch but the 12 bolt has Chevy written all over it.

 

if I recall correctly a 12 bolt has a LITTLE less drag, plus... fords suck

 

Lol, the 12 bolt is a little less drag, but nothing you'll notice. I wanted a 12 bolt for the purist reason, but then realized I could build a 9" for half the cost. HALF.

The quick change gears are nice, and I didnt think about having another set for the street....would raise my stall though. 2.73 right now in the stocker, and its poooooooooop.

 

i run a 9" and I'm extremely happy with it.

 

The quick change idea is nice but not everyone will have a second complete center section to drop in. The case can be from a junkyard but you also need a second set of gears, posi, etc. Considering how many times you may change it, most people wouldn't have that much invested to just sit around.

It's faster to swap than gears in a 12 bolt but even in a car like mine, I can't see swapping the center section in anything less than an hour.

A 9" is super simple to set up. Everything can be done on the bench. No crawling around under the car to adjust the gears. No pinion shims under the inner bearing. They're behind the pinion support so adjusting the pinion depth is an easy trial and error without having to modify or destroy the inner bearing.

As mentioned above, the HP loss difference between the 2 diffs won't be noticed unless you're class racing where you need to get every fraction of a HP to the wheels.

The 9" uses one series of carrier. That means if you find a junkyard posi with 2.77 gears on it, you can swap the gears to any other ratio without having to buy a new posi. You can also start with a mild gear and as your car progresses, you can easily just swap the gears to a deeper ratio without having to buy a different posi.

If you're worried about the weight, you can buy an aluminum center section for the 9" which only weighs 20 pounds greatly reducing the weight of the diff.

Standard 12 bolt axles are 30 spline. The small Ford are 28 spline and are non tapered so they're probably just as strong. The larger Ford are 31 spline. Larger than that and you need an aftermarket axle, case, carrier although 33 spline can be made to fit in a stock case.

The Ford axles bolt in at the backing plates and don't need c-clip eliminators if you're running fast enough to require them.

There are many other advantages to running a 9". About the only reason you need to run a 12 bolt is if you feel you never want anything related to a ford on your car (it'll be all aftermarket anyway) or you're running in a class that says you can't mix car brands (stock eliminator rule). As for the part about not running a Ford part, many people have Ford injectors for their TPI systems.

 

Thanks for all of the good input. I know from a durability factor, the 9" is every bit as good if not better. I think I am just being Ford-o-phobic. But, it sounds like its an acceptable swap in these cars.

 

I believe all the Nascar cars run a 9"...

Chevy's not perfect, fords got some things I wish I had. Like remote starter solenoids, front distributor, separated exhaust runners.

short list......oh and I liked the little triangle forward windows that spun on the old trucks....supercharge my face!

 

yes

Got it and also have a remote start button mounted on the cowl to help bump the engine over during valve sets.

Not yet but I'd like to get a crank trigger

Got it but then that's also because I have a BBC.

 

Crank trigger, for the electronic reasons or parasitic? Both?

Wait, Im thinking distributorless, unless thats what you mean....................................bedtime...

 

I have a 4th gen "12 bolt" 3.73 posi, 31 spline axles, with LS type brake backing plates
ready to install.

I have a sale pending, but I haven't seen any money yet.

If it falls thru it will be available for $1900

 

that is SICK!!!! i just have the trigger one with quick connect fittings..


9" FTW!!! but dont get the base currie junk.. go moser.. i'm having problems with mine.. like my truetrac binding up on turns and axles starting to twist with only 1.7 60ft's.. gonna get a moser third member and axles when funds allow..

EDIT: moser has a lifetime warranty on 35 spline axles.. currie has NO warranty at all..