landstuhltaylor

iTrader: (6)

Blew up the 10 bolt again, I got about 20 hard launches for each one. The rules may be changing to allow a swapping the rear, but it would still require me to run a stock 3.42 gear ratio which I can't get in a 9.

Will the 12 bolt be strong enough for this application? Looking into a 33 spline unit with a TrueTrac

370 whp
3300lb race weight
T56
315 Hoosier A7
Nasty, nasty mini-twin clutch that loves breaking **** behind it

If this is just going to be an on-going issue even with a 12 then I will just stop running Pros and launching the car until I make the move to CP/CAM a few years down the road.

SteenH

You will not have ANY issue with a 12 bolt. Especially at that power level.

toneloc60

iTrader: (7)

It's like asking if a BB gun will have an effect on a tank.

01ssreda4

iTrader: (96)

Will be fine, much better then a 10 bolt.

landstuhltaylor

iTrader: (6)

People also told me a 10 bolt would be fine for an autocross car. In a combined 14 years of running nearly every weekend, other cars have broken a grand total of 2 of them. Yet here I am, and I broke 2 in a span of three weekends. Given that it's not unheard of to break a 12 bolt with 4xxhp, seems like a valid question.

Chris Paveglio

iTrader: (2)

are you breaking them on launch? Or do they poop out elsewhere on course?

HioSSilver

iTrader: (8)

Do a 9". Way more support....stronger......probably even cost less in the long run.

landstuhltaylor

iTrader: (6)

Both popped off the launch. Already have a solid pinion spacer and TA cover on it.

Did you read the OP? I'm not interested in the 9 unless it's absolutely necessary.

HioSSilver

iTrader: (8)

Yea i read it and didn't care. Fact is you're just not gonna beat the versatility of a 9" with what is on the market today.

Even his gear ratio issued is cured. You can get 12 bolt centers for 9" housing.

landstuhltaylor

iTrader: (6)

Know of one that isn't designed specifically for drag racing? The only one I can find is the Strange unit which is advertised as being for drag racing only and only available with a spool. Both of those would not work for my needs.

I don't want to use a 12 bolt, but I would be forced to with the lack of a 3.42 gear option in a suitable 9.

blackandgold

iTrader: (2)

I wouldn't say my FAB9 is set up for drag racing, in fact my car has never seen a drag strip. But you shouldn't break a 12-bolt at your power levels.

landstuhltaylor

iTrader: (6)

It's not that the Fab9 is for drag racing, but all the documentation for the 12 bolt center for a 9 says that it is for drag racing only. My quick googling seems to confirm that with insanely short gear life if I were to put it in a 3000lb+ car. Seems to be marketed towards light drag cars that are fine with gears being a consumable, and should be used with a spool which might actually be worse than an open diff in an autocross car.

Fab9 would be my first choice if I could get a 3.42 and it would work with a Fays2. I know I could go the MWC setup but personally I prefer the design of the Fays unit. Long term plan will have a 9 in it once it goes CP/CAM, but I don't have 10k laying around to do the rest of the mods required to make the car competitive there right now. The idea would be to pick up a 12 bolt next season (if the proposed ESP class rules pass) and then sell it to fund a 9 when I make the class jump. Seems I should probably just go to Strange/Moser directly with my needs and see what they have to say.

HioSSilver

iTrader: (8)

They are probably just setting it up with a soft type drag gear.

SteenH

I always get a kick out of the people who bash a 12 bolt when they haven't owned one.

Bob@BruteSpeed

iTrader: (16)

http://shop.brutespeed.com/Moser-12-...fferential.htm

Take a look at my shipped prices on Moser 12 bolt rears. Let me know if you have any questions. Bob

landstuhltaylor

iTrader: (6)

Not bashing it. I want to own one for a time if it will work, I just want to make sure it will do the trick. Would really really prefer a 9 for the removable center as well as weight, but if a 12 bolt works in ESP it works. Figured I'd get some input from some people who may have run it with a similar style clutch.

Pulled the cover off and saw that just like I suspected last time, it was the Auburn that ripped apart and took out the ring gear. I shut it down earlier this time so there was no ring/pinion damage and shows what the source really was. Ripped the spider gear out of the Auburn on the launch. Last time I kept hammering on it for the rest of the run because I really wanted some free Hoosiers and the Auburn literally fell apart, pictures are in my last thread I believe.

So on that note, I'm planning on running a TrueTrac to finish out the season. Are they at all stronger than the Auburn in a 10 bolt application? Not planning on launching it again as I don't want to roll those dice, but I am curious.

M4N14C

iTrader: (3)

You ever compare the weight of the 10 bolt vs the FAB 9? I'm in the market for a new rear end and the biggest factor for me is weight. Last thing I want to do is add 50lbs of UNSPRUNG weight to the rear of my car...

HioSSilver

iTrader: (8)

My fab9 is only about 5-10lb heavier than my 10bolt.

blackandgold

iTrader: (2)

Weight was why I went FAB9 instead of 12-bolt or s60

This. And that's only because I didn't go with the lighter aluminum third member. In theory I can get it down below the weight of my 10-bolt.

thunderstruck507

iTrader: (18)

For what it's worth my car has had a 12 bolt with an eaton posi in it since shortly after I bought the car.

It took around 14 years of abuse drag racing, autox, aggressive back roading, and a couple light road course days. Finally the clutches wore out and it started having intermittent issues holding both tires. The Eatons, unlike Auburns, are rebuildable and the clutches are less than $100 shipped from Summit.

Granted when swapping to one in an fbody there are other factors you may consider...but the rear itself is up to the task I'd say.