Teach me about 9" rearends

[blaserman]

I always have used 12 bolts but I hear 9" is stronger.
I also see 28-40 spline axles which is the best to have , how many splines

[edvancedengines]

A built 12 inch is stronger than a factory 9 inch

The only way a 9 inch is strong is if you invest some money into it.

The more splines an axle has usually it is also larger in diameter. Larger if all else is equal is stronger.

Very few cars can be powerful enough to twist top quality 35 spline axles. I have seen above 3,000 hp on Mark Williams 35 spline with no isues. I have also see a couple of other brands damaged with 35 splines with 1,600 hp (appx) in addition to tire shake.

I prefer Mark Williams but they cost more money.

If you do a 9 inch Ford be sure to get a strong aftermarket third member case, and an aluminum pinion bearing retainer.

Ed

[lively]

THE 9" IS CHEAPER TO BUILD THEN A 12 BOLT/ THE 9" CAN CHANGE OUT GEARS ALOT QUICKER THEN A 12 BOLT----2 VERY STRONG POINTS FOR IT PLUS COMPARING A BUILT 12 BOLT TO A STOCK 9" IS NOT A TRUE COMPARISON ED :oops: :oops:[ APPLES TO APPLES AND ORANGES TO ORANGES]

NO OFFENCE ED JUST MY FINDINGS OVER THE YEARS-- :wink: :wink: :wink: -DENNIS[LIVELY]

[SST4530]

I agree with lively on this point. Dollar for dollar a 9 inch is the way to go especially if your talking relatively stock configuration. A 12 bolt traditionally takes less horsepower to turn but that's about where the advantages end. 9" is stronger, easier to work on ( I'd much rather have a third member on the bench setting up gears then rolling around on the floor or in the pits. I think also if your at the track and needed parts you'd be much better off with a 9". You also don't have to add c- clip eliminators like on a 12 bolt.

I agree with Ed that you really either need a nodular iron or an aluminum thru-bolt case, and an aluminum pinion support. Somtimes the ring gear must be chamfered so it clears the pinion pilot bearing area. :)

[edvancedengines]

Of course you guys are right. In my opinion a stock 12 bolt High Performace rear with the Hi Impact axles and Series 4 positaction is stronger than the standard bread and butter 9 inch. Factory rear ends the Dana 60 is the strongest and the cheapest as well as heaviest.

I have seen so many guys put regular 9 inch fored rears with factory regular duty carriers and retainers and be disapponited because they had read the 9 inch is strong. The factory 12 bolt is at least as strong as factory run of the mill 9 inch and the Mopar 8 3/4 is worse.

Guys without the finds to buy or to build a really tough 9 inch can install a factory Dana 60. They can also jst make the initial hit a little softer so it does not shock the rear end. For example launching on foot brake is easier on rear end.

I have built Bullet Proof 9 inch rears but it is not cheap. You will never make a 12 bolt to be fully bullet proof.

Ed

[SST4530]

If a guy can come up with a factory nodular iron case and upgrade to some Moser or MW 31 spline axles and spool you have a pretty darn tuff unit. I've run this same setup in a 3500 lb Super Street for many years and never an issue, also used the standard street gear instead of a pro gear. Same set of gears since 1990. This same setup was in the car in my avatar on that run and many more just like it.

[curtisreed]

I don't agree that a 9 inch is cheaper to build. You should probably change out the standard center section on your ordinary 9" so you would need aftermarket center section and pinion support, after that the bearings, axles, housing ends, spool, gears are not that much different in price.

That said I think 33 spline is the largest you can put in a factory 12 bolt. I will say that in my experience it is easier when modifying 9" rears and as Brian said easier to work on. Ultimately the 9" can be made stronger. I wouldn't spend the money to change out the 12bolt in my roadster but if I were starting from scratch I would go with a 9" because of the options it presents and for resale value.

Curtis

[mcracecars]

stock 12 bolt a little stronger than stock 9"
12 bolt can be beefed up cheaper than 9"
both require gears, spool , axles, and housing ends, but 9" requires beefier center pot, also bracing and inside housing welding is a good idea.
A dana 60 would be stronger than 12 bolt or 9" with comparable axles/spool/ gears.
If money is no object, then fabricated 9" housing with all the goodies would be very strong, but would it be stronger than the dana?? dont know all the big boys use the fabricated 9" or those modular designed ones.

Fabricated 9" look trick under the car, dana and 12 bolt it seems these days are passe'
In my opinion a dana 60 with axles/spool/gears would give good service in almost any car running down to 7s, or quicker if the car is light.

[signsbyesa]

i did not want to answer this one because i figured if blaserman has
been using 12 bolts for a while he should have first hand how strong
they are, or can be. I have (acording to ed) the worse a mopar
8 3/4 shortened with moser 35 spline axels w/a strange 35 spline
spool with 4:56 us gears, back braced and plenty strong for me, but
hotrod mag. had tested beefed up 12 bolt/9" and the 9" came out
ahead, and whats the answer, what ever well beefed differential,
and mopar is the worse, thanks. :(

[lively]

i have seen the 8 3/4 mopars in big horsepower cars that hold up very, very well!!!!---i prefer the 9" because i have proved them on several violent reacting cars and have very little problems if any-plus i drive my cars on the street and strip and can change the pumpkin out for the street gears quickly---THE FACTORY WAR CASE AND NODULAR CASES WILL TAKE ALOT OF HORSEPOWER WHEN THE GEARS ARE SET UP RIGHT-[ I HAVE HAD MORE TROUBLE WITH THE U-JOINTS THEN ANYTHING ELSE]--BUT THEN I AM A FORD FREAK :lol: :lol: :lol: ---LIVELY

[edvancedengines]

At one time if you looked on many of the Top Fuel cars you would find a 8 3/4 rear end. They were lighter and gave no trouble.

Fast forward to when Top Fuel cars strated getting traction and were hooking up. 8 3/4 quickly disappeared and were replaced with built 9 inch and with built Dana 60 's. Fast forward more and you find Those also began breaking and now they are using a huge pinion gear and a huge ring gear in a special made for them rear end.

All of my earlier experiences of negatives and positives with rear ends were all on clutch cars. The 8 3/4 was the weakest. Now possibly an 8 3/4 will handle an automatic car fine at a much higher power level with less initial torque hitting them or with a little tire speed.

Unless someone has recently started making them, you could not buy a 9310 Nickel gear set for the 8 3/4 and they were available for the 9 inch the Dana 60 and the 12 Bolt GM. That also is a brute strength issue.

Ed

[lively]

I always have used 12 bolts but I hear 9" is stronger.
I also see 28-40 spline axles which is the best to have , how many splines

ok---LET'S GET THIS INFO---WHAT IS IT GOING IN AND IS IT STREET DRIVEN?---WHEN YOU CAN CHANGE THE GEAR RATIO QUICKLY THEN THE 9 "OR 8 3/4 REAR IS BY FAR THE BETTER SETUP PLUS IT IS ALOT MORE READILY AVAILABLE IN THE MARKET PLACE 8) -NO FORD OR CHRYSLER BIAS BEING SHOWN JUST BASIC FACTS[ NOT EVERYONE CAN SPEND 1000'S ON REAR END SETUPS--I HAVE HAD THE SAME 9" IN SEVERAL CARS OVER SEVERAL YEARS WITHOUT FAILURE[ I RUN A FACTORY WAR OR NODULAR CASE AND 31 SPLINE AXLES]---SORRY BUT I STILL LIKE THEM BETTER--YES I THINK THE DANA 60 AND THE FABBED REARS ARE FANTASTIC BUT THE ARE VERY, VERY EXPENSIVE FOR THE AVERAGE GUY---MY 2 CENTS WORTH --LIVELY

[BY THE WAY ALL OF MY CARS WERE 4 SPEED CARS] :lol:

[blaserman]

I am finding a 12 bolt for a chevelle hard to find , and price is getting crazy. Most people want as much for a stock 12 bolt , as for a fabracated one on very close. I am leaning towards a 9" w/ 456 gears and a 30' tall tire. I am building a 632 10/1 motor . 400 turbo .I will drive on the street , but you know it has to go to the track and see what it will do.
I live near Auto fab and will use most parts from them . My friend is building a Chevelle and his rear set up is the same . I am letting him work his bugs out on his set up and I will have less work on mine.

[lively]

THAT IS SMART---LET HIM BE THE TROUBLE SHOOTER :lol: :lol: :lol:

[suicidebomb]

I*ve gota plain old 9-inch out of a 67 f-100 in my altered, no nodular case,a strange spool, 31 spline moser axles, new bearings throughout, and less than 900$ flange to flange. I buy parts at retail. My car is light. but I don*t understand 3000# race cars. I think the real beauty of the ford ,is you can change ratios quickly, they*re reasonable price wise, and any moron can build one. I am living PROOF! If you*re making TONS of torque, 4 digit horsepower, and a heavy car, then by all means go out and buy the biggest, baddest, toughest, rear end you can afford! you WILL pay for it. Please, don*t take any offense if you have a heavy car, as I meant none, we all build what we want.
P.S. What is a WAR case?

[blaserman]

By the way this is a WHAT I CALL A STREET CAR, FULL BODY <FULL INTERIOR < RADIO ECT Not a race car.

What is the best spines more or less as in 31 or 35 splines.

[suicidebomb]

JMO, either a 12 bolt or a 9" will probably be fine for you on the street, But if you are going to WOOD IT, every time you leave a stop, you might want a dana 60. If I had a 632 cu. in. on the street, the state would take my license. :lol: No way I could resist the temptation. 35 splines are stronger than 31s but don*t know if they*ll fit in a factory carrier. Hey, keep it cheap, you*re going to buy lots of expensive gasoline!

[sg5492]

Dana 60 is the way to go. I have a ton of money in my 9" that is in my 69

[kwkracing]

Ford nine inch is the only way to go, stock or not!

[olds48]

Hp difference between a 9 and a 12 is minimal.Like 3%,is what Strange claims,but a 9 will probably be lighter.But who cares about 10-15 lbs of rear end weight on a "street" car?Everyone claims a 9 is real strong,and I have one in my car cause my buddy gave it to me and it was already narrowed to what I needed.Used to run a 8.5 10 bolt with street gears and stock 28 spline axles.Drove it on the street for about 7-8 years like that,then took it to the track for about 100 or so 1/8 mile passes.Car is 3400 lbs(don't get me started,Earl :D )and has about 625+ HP.Never a problem with the "puny" 10 bolt.I'm not impressed with the 9,to be honest.I know you can swap gears fairly quick(no quicker unless you can afford a whole nother pumpkin) and they do hold up,but they seem thin to me.You can't brace the spool bearing in them like you can a 12 or Dana,no way to get to them.Pinion stem seems kinda small(10 bolt and D60 has same dia. stem,10 bolt has one extra spline)only thing I think they really got going for them is the bearing support for the rear of the pinion(next to the ring gear).Bearings are smaller than what was in my 10 bolt and bearins cap are smaller,too.Plus they look like thay are cast from some pretty cheesy 3rd world junk,real poriuos(think I spelt that wrong :oops: )I honestly believe stock for stock that my 10 bolt was a far better rear than my 9".12 bolt will be even stronger.Had it to do over,I'd definitely go Dana.JMO

[suicidebomb]

Eric, I dont like losing the same battle twice! :lol: I do run a nine, and it is holding up so far. I also have an extra pumpkin for gear changes, but I wouldn't think about changing it at the track,I know other guys do it. I dont see that as any great incentive to run one. If I had it to do all over again, I'd put a quick change in mine, more than strong enough for any motor i'll ever run. And if I want to go from 1/4 to 1/8 mile gears I could do so super quick. Shucks, I might even have some paddle tires made, and go sand draggin. :shock:

[olds48]

Paddles???Now that would be fun :D