[FrankieT/A]

Looking for opinions on the strongest 12 Bolt center section.

I went to the track to see what this car would run...

First time out on the third run I broke an axle in my 3.42 posi 10 bolt.

I put in a stock 12 Bolt that had an existing Eaton center section. I installed Strange 30 spline axles, a Strange pinion yoke, studded the caps, put in a 3.73 Richmond gear and a girdle cover.

Third run, broke the spider gears and lunched the center section. So, here we are...I need a new center section and new gears. I was thinking Moroso Brute Strength or maybe a Detroit Tru-Trac. This car is mostly driven on the street but if I'm in there I might as well do it right. If anybody would like more details just ask. all opinions welcome.

[opeliac]

Ive seen Eatons hold up behind some decent power, in heavy cars...

How heavy, and how fast is yours?

[FrankieT/A]

Originally Posted by opeliac

Ive seen Eatons hold up behind some decent power, in heavy cars...

How heavy, and how fast is yours?

Hard to say "how fast?" cause that's what I'm trying to figure out. Last time I weighed the car it was about 3800lbs. but I think its a little lighter now maybe 3600lbs.

This is a manual car so... At the beginning of T&T the car doesn't hook. As soon as a bunch of cars run and the track gets sticky my car dead hooks. Then things break. I have a pretty strong tranny so so far it has taken the abuse. The car all along has had 1350 U joints so they too have dealt with the abuse.

[Scott65]

I'd be looking for a Dana 60 for a standard shift that you plan to "dead hook". Watched a buddy fight this battle behind a small block Chevy. Not good. Trashed 12 bolts and 9 inch fords. Finally found a Chrysler 8 3/4 that held up behind the small block. With the torque of a Pontiac I'd move straight to the Dana 60. Or change to street tires, or an auto... Good luck with it however you decide to go. And yes, the Brute Strength is probably the best clutch type unit.

[opeliac]

Again, are we talking about dumping the clutch on a 600HP engine?

If so, what transmission are you running?

If its big power, switch the posi to a spool with bigger axles, and never look back...

[Scott65]

Then add billet steel caps, and studs, and a girdle, and then cross your fingers...

[FrankieT/A]

Originally Posted by Scott65

I'd be looking for a Dana 60 for a standard shift that you plan to "dead hook". Watched a buddy fight this battle behind a small block Chevy. Not good. Trashed 12 bolts and 9 inch fords. Finally found a Chrysler 8 3/4 that held up behind the small block. With the torque of a Pontiac I'd move straight to the Dana 60. Or change to street tires, or an auto... Good luck with it however you decide to go. And yes, the Brute Strength is probably the best clutch type unit.

This is an LS motor with Street tires...Dana 60 would be nice though...

[FrankieT/A]

Originally Posted by opeliac

Again, are we talking about dumping the clutch on a 600HP engine?

If so, what transmission are you running?

If its big power, switch the posi to a spool with bigger axles, and never look back...

I'm guessing like 500+ and the trans is a SS700 Keisler (Liberty).

This is a street car so not so warm and fuzzy with a spool.

[Gary H]

Years ago I ran a Moroso Brute Strength posi in a 10 second Firebird with an automatic. Granted it wasn't a manual transmission , but I had several hundred runs on it before it broke a spider gear. I did however, break several ring and pinions during that time. After I broke the spider gear, I installed a spool and never broke a ring and pinion after that. I think the posi unit had a little flex to it compared to the spool and that was the difference

[ponjohn]

Truetrac?

[opeliac]

Originally Posted by FrankieT/A

I'm guessing like 500+ and the trans is a SS700 Keisler (Liberty).

This is a street car so not so warm and fuzzy with a spool.

Well, if you buy a bad ass posi, it'll drag one tire on a turn...I drove my spool year round here in Kentucky, for years...Big tires on the back, 3 1/2s on the front...Never had an issue...

In fact, there are numerous big powered street cars that have spools...

To be honest though...We have hit some Eaton units, in 1/2 ton trucks with some hefty nitrous kits, and they lived...I wonder if you just had a bad unit.

[Stormin]

I use a mororso brute strength carrier.
The same one has been in the car for MANY years!!!

The car is an automatic with a 4000 converter.... yes.. I drive it on the street... big tires on the back. No issues whatsoever.

Car is lighter and faster than it was before...but...even so... car was 3500 lbs..ran 10's.

If I needed something stronger at some point.. i'd definitely go with a 9 inch. but.. .but i'm pretty comfortable with what I have for now.

take care
NB

[Mike Davis]

Ran a Moroso Brite strength for years in a 3700lb car without issue running low 10's. After I started running in the thigh 9's went to a spool.
Are you running a support cover?
Back in the 80's I worked for a Pro Stock racer named Jim Kinnett that ran a Hemi Powered Lenco Trans, Plymouth Volare. He ran a 12bolt in it as it took allot less power to turn.
They will live if set up right.

[Stan Weiss]

Originally Posted by Mike Davis

Ran a Moroso Brite strength for years in a 3700lb car without issue running low 10's. After I started running in the thigh 9's went to a spool.
Are you running a support cover?
Back in the 80's I worked for a Pro Stock racer named Jim Kinnett that ran a Hemi Powered Lenco Trans, Plymouth Volare. He ran a 12bolt in it as it took allot less power to turn.
They will live if set up right.

Mike,
That is bring back some memories. I remember him dominating with his SS Hemi car.

Stan

[steve25]

Did both spiders give up on the cross pin?

[Mike Davis]

Originally Posted by Stan Weiss

Mike,
That is bring back some memories. I remember him dominating with his SS Hemi car.

Stan

Jim knew how to make a Hemi run. He lived about 2 miles from me and had a Auto parts store and a really nice machine shop. I started working in the machine shop when I was 15. As a car crazy kid I was in heaven seeing all the SS and Pro Stock engines rolling out of that place.

['ol Pinion head]

The original spider gear/ side gear combo used in nearly all original Muscle Era 12 bolt Eaton posi units had a 10/18 count. That particular combo's metallurgy was & is a JOKE. Have to remember Chevrolet began putting 12 bolts in their vehicles when at around the 300 gross hp/torque level, there's a HUGE difference in the internals in a garden variety 12 bolt posi rear & one that was built to be abused at the track/ came in a handful of '69 COPO 427 cars.

Special heat treated 10/17 spider/side gear combo's were avail from Tom's Differential, over the years I've bought numerous sets to rebuild OEM 3 & 4 series Eaton carriers. Have not ordered any since Tom Watt passed, but Tom's has a new website design & is selling parts, that spider/side gear set should still be avail, as well as thicker plates & 400lb springs.

Eaton TopSpec/Moroso Brute Strength carrier are a very strong 4 series posi carrier, the spider gear/side gear combo are mfg out of a very high quality tool steel, much more strong than what Chevrolet offered in their HP Service packages kits over 4 decades ago. the carrier is built with 22 steel clutches wo the slots in every other clutch, you have to buy Moroso "Climbing Lube" for this style of clutches & preload. Have installed half a dozen of the Brute Strength 12 bolt carriers into customer cars rears over the years, 2 went into early Camaro's dipping into the 9's, the remainder went in rears in 10 & 11 sec GM A-body's. Will double ck a Brute Strength carrier later this week, was installed in the mid 70'swith some 4.10's in one of my '71's rears. believe the spider/side gear count in the Moroso carrier is 10/16, going to pull it out anyway & set up with a set of thin Richmond 3.73's, most likely dial back the preload some w 400 lb springs.

[FrankieT/A]

OPH,

All the parts are still available from Eaton through Summit. All the parts I need are around $300.00 not including R&P. Am I better off replacing the parts I need or just buy a complete new unit for $569.00? Is the new Eaton unit overall better? I would be replacing the spider gears with 10/17 heat treated gears and 400# springs.

['ol Pinion head]

Frankie, for the power level I believe you're at, I'd order heat treated 10/17 spiders & the good steel clutches from Tom's Differential. with a new Eaton 3 series carrier from Summit, believe you're going to be getting carbon fiber clutches.

[455-4+1]

My old street driven TA from 20 years ago ran a stock 12 bolt carrier with a Powertrax bolt in centre (several springs available to tailor the hardness of the engagement)
We broke driveshafts, 1350 series Spicer yokes, gear sets and axles LOL, but never the centre section or PowerTrax !!
30" ET Streets and leaving off a 2 step at 4500 RPM, flat shifting each gear. It smashed the tyre pretty hard on a dead hook, and would even pull the fronts shifting into 2nd which was pretty good for a pump gas 455 with a flat tappet hydr cam and 6x heads

Car weighed 1850kg (over 4000lb) so was no lightweight

I think helping it live was a sintered iron clutch disk with an old Hayes 12 post slider clutch. we could cut the static weight in 1/2 with this setup, and it would still lock up with adjustable centrifugal assist (via weights), but slip a little on launch and shifts. We tried a flash new kevlar linned, aluminium backed clutch disk from Hayes, it didn't last a single meeting !!!!