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Discussion Starter #1
Ok everyone. My previous topic raised a bunch of questions. I have been talking to a local transmission shop in the Seattle area about building a 12 bolt for my '68 (soon to have a 509 ci with 540HP and 580 ft-lbs, and TH-400 transmission.) I have goten an "around $2500" estimate.
For this amount of torque, should I be looking at a 9"? My understanding was that 12 bolt could be strong enough to handle this amount of power plus more. What is your feeling on the $2500 estimate fot the 12 bolt?
You input will be greately appreciated once again.
Thank you.
 

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no matter how you look at it, that is a LOT of money for a rear end. if you look in the right places you can find 12 bolts in good/rebuilt shape for $1500 and much less. im not an expert but the way I see it, with the turbo 400 you wont be doing any 6-8000 rpm launches which is when you need a real strong rear end because of the car hooking up. if you could make more power with a ford engine would you use that instead of a chevy?
thats how i look at it, plus the price is going to be jacked up because it has to be custom fit with width and suspension brackets..

also we need to know more info on your stall converter and how you plan to use the car.. if this is a driver, id say no way, go with a 12 bolt.
 
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$2500 for a 12 bolt, wow! That must be some rear. You can get one from Mark Williams for less money, we are talking street here are we not???

What makes you think you can break one up on the street? If it were a stick car, maybe.

Everything about the 9 inch Ford is more money, the gears, the pinion support, axles, and on and on. The rear requires more hp just to spin it, a lot more than a 12 bolt.

Stick with the 12 bolt and find somebody that's not on drugs to do it.
 

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Discussion Starter #4
Thanks for your input guys. I will be driving my car 3-4 days a week, and occasionaly race it (once or twice per year!)
I am taking the car in to the transmission shop next week to have the transmission build and installed. The plan is a 2400 stall converter, and I was thinking 3.73:1 gears on the rear end once we are ready for it . Mike you are right, I will not be doing anything to even close to 6000 rpm, so I think that a well build 12 bolt will work. The $2500 includes installation by the way (I am not brave to atempt this by myself yet. I just put power disc brakes to the car, and that is how far I feel comfortable going.)
Thanks everyone.
 
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Wally,

Here is a break-down of how to spend $2400.00 on a 12 bolt.

- 65 Chevelle bare housing $150.00
- Girdle cover w/ axle stess bars $175.00
- Billet caps (both sides) $107.00
- Labor to install caps $40.00
- Gears $130.00
- Labor to set-up gears $110.00
- Labor to modify housing $552.00
- Mark Williams internals $1100.00
That total $2400, which does not include brakes!

The labor to modify the housing included a slight narrowing (1 or 2 inches), relocating lower control arm brackets and coil spring mounts (from 79 G-body 7.5 10 bolt), and installing billet housing ends with captured bearings (like 9" ford).

The Mark Williams components include 35 spline axles and spool, billet housing ends, 11/16 drive studs, axle bearings and retainer plates, and gear installation kit. (Excellent quality stuff BTW)

This is much more than is needed for a street/strip car, but is suited for trouble free drag strip use. The only other thing that could be beefed beyond what I have done, is to replace the axle tubes w/ chromoly tube, and a billet pinion yoke.

My plan was to never have to replace broken rear end parts.

Todd G
Malibu Muscle
http://www.qis.net/~tgeisler

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I have to question what Wally said, as far as parts go the 9in will cost as much if not less than a 12bolt as far as internals go. Sure wellding on all the brakets and modifying it to fit the car will jack the cost up. All the Nascar guys use a rear based on the 9in Ford which must mean something about its durability. Also it is nice beingable to work on the rear assmebly out of the car with out pulling the whole axle. If money allows I will be putting a 9in on my Chevelle, I have one in my truck and it has done very well through years of my abuse.

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JT
71 SS 350 soon to be Vortec 355 then a 454
www.angelfire.com/co/KellyMotorsports
 

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Wally,
From experience with the 9 inch ford and 12 bolts the 9 inch requires less hp to turn then a 12 bolt.The cost factor is on the ford side as well.Why do you think its a favorite among drag racers?
 
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The only reason drag racers use the Ford is pure ease of the swap. If strength is what you are looking for, it is the Dana 60 that rules, followed by the DORF 9 inch with a 12 and 8 3/4 chrysler tied for third.

As for the hp thing, look at the design of the rear, the gear intersect angle is at the bottom of the gear, takes more power to spin it, ask Mr. Williams, he is the one who told me.

Don't get me wrong, I love Mark Williams stuff, best you can buy and if money is no object then go for it. But for the average street car that may see a trip down the 1320 once in a blue moon, it is over kill.

Let me put it another way, 8000 rpm starts with stock 12 bolt stuff, 9 inch slicks, never broke anything.

14 inch tires, 5500 converter, Henry's axles and spool, never broke anything. A lot less than 2500 for the parts.

[This message has been edited by Wally (edited 05-30-99).]
 

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Wally, Just curious. Were the 8000 rpm starts with 9" slicks ( NHRA stocker) with a stock posi, modified posi, Moroso Brute Strength, spool, or ? I have a Chevelle 4 sp with stock 12 bolt posi and wonder how much it can take. I know the Muncie would probably give it up first, but how strong is the stock posi? I used to run a Corvette NHRA Stocker and I had a load of broken IRS parts until I installed huge Henry's Axles half shafts, yokes, and a spool. Luckily it was an automatic or that wouldn't have lived either. With the stock half shafts I ran a Moroso Brute Strength posi with no problem. von
 

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Yanniz, since I feel like I helped you start this whole debate, I'll finish it right here and right now. A stock 12 bolt is stronger than a stock 9". Do stock 9" have nodular iron carriers. No, most don't. So there is one upgrade that you must make to make them equal. Why does NASCAR use 9". "It's the carrier, stupid". ( I don't mean anyone in particular, it's just a saying). The easy gear swap by having ring/pinion in a center carrier is the engineering design of choice of all racers, even drag guys. Finally, it's supply and demaind. There alot more stuff available for the 9" beacuse of demand for the reason stated above. Simple economics.So there you have it. The 9" is no stronger in stock trim. It does have an engineering advantage in the removable gearset, which is why racers use it. Yanniz, you might be able to piece togehter a 9 cheaper due to supply demand. Unless it's an original car, no one is going to fault you for saving some $$ for the same functional utility. Sure I prefer Chevy, but really! $2500 sound steep, but I know these things ain't cheap. Here in the NE a 12 posi will go close to a grand. My kid bro lives in AZ and parts are more there. You might want to look around for used, but then it might cost you just as much if something's not copasetic with the rear. I don't think you'll need allot of high speed high $$/Strange/Williams for your application. If you go with a 9", it'll have to be stronger than a stock one. Good luck.

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I'm running a 9" from Moser, boxed in the control arms, and put in poly bushings....no hop and you can do it all yourself.
They built-in a few extra degrees into the pinion angle and that kinda "acts like no-hop bars".
I put in a Detroit locker, and I love it. No more concern about "clutches". Your rear axles are locked until you make a turn. The new improved model doesn't "clunk" either.
Plus, you can drop the third member and change gears... yourself.
Cost... 300.00 housing, 300.00 axles, 150.00 gears, 400.00 locker, 65.00 third member from the yard.
Use the F*** long pinion yoke and you don't have to cut the drive shaft!
Phil
 
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Von, it was indeed a stocker, E/S on 9 inch tires. Man I love that 302, rpm is damn near unlimited, with 86 lbs. of spring pressure on the seat and 206 open. In my day stock meant stock. The rear used a type 4 carrier, 5.86 gear and stock axles. We were allowed to use slapper bars, Lakewood was the traction bar of choice.

10.80 at 113 to 114 was the best I could do. Lunati made the cam that brought this baby to life.

All I did to the carrier was shim up the posi unit, never broke anything. Now when I changed the deal over to a SS/I car, that was different, spit all the teeth off the pinnion at York Pa., never broke the beam.
 

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Go to the drag strip and look at the really nice clean and fast cars. Pass up the junkers. In my town as well as at all the NMCA and NSCA events I've ever been to about 90% run 9 inchers. Why? Ask them. I have my own opinion and generally it is about the same as the fastest guys in the world with street cars as to why the 9 inch is better. I'm no expert but they are. Make up you're own mind but if you go with a 12 bolt you will definately be in the distinct minority. I only wish you were close to me as I'd sell you my 12 for a lot less than $2400 so I could build a 9
Remember this is not just me talking here but the fastest nicest cleanest cars in the world almost all use the 9. I'm sure they don't do it for looks . They do it because the 9 is better. Just ask them...
 
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The only resemblence to a 9 inch DORF rear that the "worlds fastest and cleanest" cars use it the ring and pinion, and even those are different for the pinion supports they use. Every piece, and I do mean every piece is purpose built, the housing, the pumpkin, the pinion support system, axles, housing ends, the whole deal.

An earlier post had it right, in stock form the 12 is a better deal all around.

This is a good example of why they make different flavors of ice cream, it would be a dull place if everyone liked one flavor.
 

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Or at the strip with his setup. If Yanniz wants to go brand new, however, setting up a 9" may indeed be cheaper. Oh, Yanniz, I didn't mention before, there are alot more gears available for the 9". Again, the supply/demand economics I stated prior. Man, I didn't know this would be so controversial -- Cool! Anyway Yanniz, my car isn't the cleanest or fastest, just an original '67 Chevelle with a nasty little 427. Can't wait to see how this nasty, unclean bitch runs! Price out a complete 9 for your setup. I bet you don't break $2000. You should be able to do a 12 used for half that. No labor included.

I digress, but I've seen the "gotta have the trickest syndrome" in many things, sports, firearms, etc. It just ain't a game I feel the need to play. Go with what is sure to work at the best cost. For you that's a stock 12 and a slightly mod 9".



[This message has been edited by Gene Chas (edited 05-30-99).]
 

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One last word. I just re read the original post. Yeah I would stick with the 12 if the car only saw strip duty twice a year or so. Stick w/ the 12 on the street. Problem is, speed is addictive. I once thought it was sacraligeous[sp?] to tear a car up on the strip. I had a 5.0 for the street and I thought slicks and race gas was "cheating". Nitrous was for woosies. Well, the speed bug hit, the 5.0 went and the Chevelle now is becoming a full blown race car with a fuel cell, slicks, roll cage, race gas etc. Even though my new motor will make about 625 hp on the motor w/ 1000hp on the gas, I'm already planning for the Donovan block, Pontiac headed monster for my next motor. The point is... this " 1 or 2 times to the track' thing can get outta hand real quick. It did for me at least. Who hasn't gone way beyond what they originally thought was "fast' and in the end spent twice the amount of money? Hell, I had to sell my 5.0 and get my Chevelle to find that out. Shoulda bought the Chevelle in the first place but I never knew it would go this far. I think everyone can see my point.
But yes, I see others as well. If it is a street car and always will be then go for the 12. If the speed bug hits, you buy another daily driver, pull this one to the track on the trailer and the 12 breaks because this motor isn't enough for you, remember this thread.....
Off my soap box..
 

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The 9 inch ford is just better it has 3 pinion bearings one on each side ring gear and one near the u joint. The 12 bolt retains the axle shafts with c clips inboard the drive splines the axle bearings use the hardened area on the axle for a inner bearing race. The problem is hardened metal= brittle metal and if the axle breaks anywhere the wheel and axle leave the car usually taking the quarter panel with it and theres more when the wheel leaves good bye brakes NG. you can make a 12 bolt work but its not cheap. I bought a 9 inch with 35 spline axles strange center section datona front bearing,detroit locker .500 wheel studs complete delivered near me for$2800.00
made to bolt right in with brakes just install and bleed brakes and wella no more broken parts bullet proof to 1500 hp . The bal& blue printed L-78 396, 450hp brigs& stratton can't break it I have tried just my .02 .
 
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