9" or 12 bolt?

[1badchevelle]

I am looking so see your thoughts on what would be better. I have a 71 chevelle that is my daily driver. I have a 10 bolt non posi in it know but looking to go with a 12 bolt. I have seen several chevelles here with 9" fords. what if any is the denifit? Ihave a mild mannered 350 with a 650 barry grant, hokker headers, accel ignition, edelbrock intake and a mild cam. with a th400 behind it. Also I will be going to a c6 brake set up, what rear would be best and gear ratio(remember daily driver)

[Gordz32]

The way I see it is 9"'s are just way easier to work with, and cheaper than 12 bolts. I f you wanna keep the car all chevy, go with a 12 bolt.

[MrQuick]

I'd just build that 10 bolt up. 71 it should be an 8.5" and there are a lot of parts available for it.

[Shawn MacAnanny]

I think your 8.5" will be just fine. I'm not worried about mine. I'll be installing c'clip eliminaters and axels eventually but right now im not worried about it. I'm running a stock posi and 4.56 which will be seeing 420rwhp with a 6 speed. Once the axels and c'clip elimiters are installed it'll see 480rwhp+ and a 150shot. There are guys in the 9s on them. They are just as strong as a 12 bolt. The pinion diameter is actually wider too.

[Apogee]

Personally, I'm not a big fan of c-clip eliminators due to the fact that they typically limit your brake options and would all but rule out C6 brakes. If it were me and money wasn't an issue, I'd run an aftermarket 12-bolt with Ford 9" big-bearing outers (Torino), giving you the best of both worlds for a daily-driver. I like that the 12-bolt runs more efficiently than the 9" due to the higher pinion location, which also means better driveline angles. Posi options for the 12-bolts are better, but having broken a Ford Trac-Loc I'm somewhat biased there.

All that said, I agree with Vince up above. The 8.5" 10-bolt is probably more than adequate for what you're running...but I understand it can be hard to sink money into a 10-bolt in the form of a posi, axles, etc when you can spend so much more on something as cool as an aftermarket rear axle assembly.

Tobin
KORE3

[MrQuick]

I've never had any luck with the eliminators either. What I've been running lately are the Chevy ends that use large Ford bearings and plate retainers. With the Chevy bolt patters you can still use Chevy brakes.

http://moserengineering.com/Pages/Housing-Ends/housingends.html

I run the 7900FM (not listed) and they work great. FM= flush mount
Give them a call for all that you would need.

[andrewb70]

Actually on e lowered vehicle the 9" will position the pinion lower, which generally improves driveline angles.

Andrew

[ProdigyCustoms]

We sell a lot of Moser and sell mostly 12 bolts for Camaro / Chevelle applications. Either a 12 bolt or 9" can be built plenty strong, it is really just you personal preference. Many like to keep their car all GM, I am one of those guys also. Cost is about the same on either set up.

As the others have said, no matter what rear, the Ford (Torino) or (new style Big End) is the way to go.

[70camaro406]

I agree with Frank. I personally have an 8.5" in my Camaro with a really nice posi unit (Powertrax). I am planning to keep my rear, change gears and install new axles, and remove the c-clip eliminators (they are prone to leaking anyway) and install Ford ends on the axles. My delimma though is I'm not sure what to do first. Get wheels and tires (285/40-17s) or do the rear. I was going to narrow the rear an inch or two for extra clearance, in case I want to go to 315/35-17s or even 335/30-17s later.


1badchevelle, if I were you, I'd keep the 8.5". They can take plenty of abuse even in stock form, and since you have a mild 350, I wouldn't waste the money on an overkill rear. Spend the money on a posi unit and other upgrades that will make it a better driver.

[69LT1Nova]

8.5". It'll handle a lot of chit. Upgrade to posi. I've seen 10 sec 1/4 mile cars with 8.5"s. Just be sure you don't have an 8.2" (although I think your year of Chevelle was 8.5" stock).

I'm running an 8.5" in my Nova.

[Derek69SS]

I'm pretty sure all 71s had 8.2" 10-bolt stock. 8.5" came out in '72 IIRC.

I'm with Andrew on this one... 9" helping fix the driveline angles on a low car is a big contributing factor to why I will be going with one. The other contributing factor is the price. :)

[Apogee]

How low is this Chevelle out of curiosity? Andrew has a good point about pinion angles depending on how low the car sits, so maybe it's safe to assume that it's in the weeds, all things considered...

Tobin

[HWYSTR]

If the rear you currently have needs to be rebuilt, it's going to cost roughly in the same area as a replacement 12 or 9, so it just makes sense to get a new replacement. You'll be sure that the housing is true that way, and can get whatever ends on it you like. Personally, I would lean towards a 9, though I did a Moser 12 in one of my cars and am totally happy with it.

[70camaro406]

I'm pretty sure all 71s had 8.2" 10-bolt stock. 8.5" came out in '72 IIRC.

In Chevelles, 8.2" 10 bolts were used up to 1972. In 1973 (and newer), they had the 8.5" 10 bolt.

Camaros, however, got the 8.5" in 1971. I still have the original 8.2" that came in my '70 Camaro, and I also have 2 8.5" 10 bolts from later 2nd gen Camaros.

For his usage, the 8.5" will give him plenty years of trouble-free service.

[Marcus SC&C]

The 8.2" is fine for a mild 350 as long as it`s in good shape. I`ve had a few in cars with healthy big blocks that help up for years. BUT I never put slicks on them. Put slicks on it and hammer it enough and you`ll eventually break it. Same goes for a stock 8.5" or 12 bolt,they`ll just take longer. If you have to rebuild the rear,change the gears and get a posi carrier you may as well upgrade. There is no all GM or Ford concern here. The new 9" from places like Currie don`t use one single Ford part, neither to new 12 bolts use a single GM component. I`d be more concerned about if the parts were made in the USA at all. If you get a 12 bolt forget about C clip eliminators,they`re a PITA and they leak. Get 9" Lg. brg. Late model (Torino type) housing ends and axles. Now you`re half way to a 9" anyway, you may as well go the extra step and get a modular center section and a pinion gear supported on both ends and get a whole 9" rear. If it bothers you not having a GM Salisbury type rear end cover just get a Currie Track 9. It`s their ultra rigid NASCAR housing with a bolt in inspection cover ala GM. It`s there to allow race teams to inspect the gear wear and mesh without pulling the center section but it looks for all the world like a GM 10 bolt cover. They do them for a bunch of applications and we`re working with them right now to do a ProTouring 9 version with double shear upper mounts and specific Currectrac upper arms with their excellent greasable Johnny Joints on both ends. Mark SC&C

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[1badchevelle]

Thanks for all you help. After talking with Tobin@ Kore3. I will be picking up a 12 bolt from a buddy. I will go with a posi upgrade and to 31 spline. I will also be going with a c5(maybe a c6 z06 set up) I have a 1" in drop and will be looking to change to a 3" afterall its a daily driver. I would consider the 9" if I decide to go air ride.

[MrQuick]

cool, can't go wrong with a 12er