9" vs. 12 bolt...Interesting Observation.
11-05-2007, 04:54 PM
#1
9" vs. 12 bolt...Interesting Observation. Just a heads up; this is NOT a 9" vs. 12 bolt thread, just an observation that I noticed while reading up on the two.
Anyway, it's obvious to anyone that has looked into an upgraded rear that either a 9" or 12 bolt is lightyears ahead of the stock 10 bolt. Also, for most that have done reasearch on the two, espeically on this site, it seems like the 9" is the more preferred of the two. Atleast that is the conclusion I came to.
Onto my observation. I was reading through an issue of GMHTP that had a LS1 shootout in it. Basically it's reader's that write in and then participate in a drag racing event that involves forced induction cars, NA cars, etc. I am sure most of you have read them. I noticed that almost all of the cars were using 12 bolts. It kind of seemed odd considering I was under the impression that the 9" was more of a drag racing rear and also just seemed more popular. So I took a look at another 2 issues of GMHTP that had the same kind of shootout. Sure enough, about 8 out of 10 of the cars had 12 bolts.
I am not knocking 12 bolts in anyway, just wanted to see what you guys thought about this.
Any input is welcome.
Anyway, it's obvious to anyone that has looked into an upgraded rear that either a 9" or 12 bolt is lightyears ahead of the stock 10 bolt. Also, for most that have done reasearch on the two, espeically on this site, it seems like the 9" is the more preferred of the two. Atleast that is the conclusion I came to.
Onto my observation. I was reading through an issue of GMHTP that had a LS1 shootout in it. Basically it's reader's that write in and then participate in a drag racing event that involves forced induction cars, NA cars, etc. I am sure most of you have read them. I noticed that almost all of the cars were using 12 bolts. It kind of seemed odd considering I was under the impression that the 9" was more of a drag racing rear and also just seemed more popular. So I took a look at another 2 issues of GMHTP that had the same kind of shootout. Sure enough, about 8 out of 10 of the cars had 12 bolts.
I am not knocking 12 bolts in anyway, just wanted to see what you guys thought about this.
Any input is welcome.
11-05-2007, 05:11 PM
#2
TECH Fanatic
I would expect this. If you have a guy that knows how to screw a 12bolt together... you dont have half the related problems that the majority of this site complains about. It kinda related to certain differential builders... if you haven caught onto that one yet.
Then again... when both the 12bolt and 9" are equal in a price range and power level they are rather compariable units... but beyond that price and power level equality, the 9" become's far superior for that specific application. Its design differences really come into play and its strength takes the lead from any rear loaded differential.
Then again... when both the 12bolt and 9" are equal in a price range and power level they are rather compariable units... but beyond that price and power level equality, the 9" become's far superior for that specific application. Its design differences really come into play and its strength takes the lead from any rear loaded differential.
11-05-2007, 06:55 PM
#4
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In the early days of the LT1 and LS1 scene, 12 bolts were more popular. The 9 inch became popular in the late 90's once more folks started running in the 8's, and then finally in the 7's. And you will still find that some folks will prefer to run a 12 bolt for an all motor car because it's generally lighter.
11-05-2007, 07:06 PM
#5
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after years of racing and working on cars, i have come to a few conclusions that i tink are rather accurate about the 9inch vs 12bolt argument.
#1 Neither is really the wrong answer
#2 Neither has ever really been shown to be much stronger than the other, just depends by whom and how well the unit was assembled.
#3 The 12bolt saps a little bit less power than the 9inch
#4 Gear changes do not involve rear changes with a 9inch. This is important if you race constantly and are apt to change your combo to exactly match track conditions
#5 They both cost a bunch of money to build "right"
it is really a choice of personal taste, i would equate it to coke vs pepsi in that regard. personally, i tend to lean towards the 12bolt for the simple reason of internal efficiency. very few of us make the power to worry about which is or isn't the ultimate as far as absorbing brute power, but rather making more common man level power we can make better use of the little bit of extra power that can be lost turning a 9inch.
like i said, my observations over the years. i stand by statement #1 though. both are good choices
#1 Neither is really the wrong answer
#2 Neither has ever really been shown to be much stronger than the other, just depends by whom and how well the unit was assembled.
#3 The 12bolt saps a little bit less power than the 9inch
#4 Gear changes do not involve rear changes with a 9inch. This is important if you race constantly and are apt to change your combo to exactly match track conditions
#5 They both cost a bunch of money to build "right"
it is really a choice of personal taste, i would equate it to coke vs pepsi in that regard. personally, i tend to lean towards the 12bolt for the simple reason of internal efficiency. very few of us make the power to worry about which is or isn't the ultimate as far as absorbing brute power, but rather making more common man level power we can make better use of the little bit of extra power that can be lost turning a 9inch.
like i said, my observations over the years. i stand by statement #1 though. both are good choices
11-05-2007, 07:21 PM
#7
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was this for the true street shootout, or the drag radial/all motor shootouts? From the races that ive been to, i havent really seen too many all out race cars that run the 12 bolt, mostly just for the simple fact of how easy it is to change out center sections in the 9 inch.
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11-06-2007, 12:46 AM
#10
I am a GM fan but maybe some people might choose a 9'' because it might help with weight distrib and as previously mentioned it is better for gear changes. Could a larger market also have something to do with this?
For those that switch between 1000ft 1/4mile and 660ft tracks maybe the 9'' is the only option. Maybe they are racing under more varied conditions. Or they are still experimenting on their set up and a gear change might be needed later in the buildup to stay competitive during the season.
For people like me I've never had a 9'' but plenty of 12 bolts and I don't switch gears alot. So I will stick with what I know as it is less hassle to learn something new. I have enough to do already and would rather leave it to the more daring members of this site!
Maybe the reduced power less of the 12 bolt will help my highway MPG. Just kidding!
For those that switch between 1000ft 1/4mile and 660ft tracks maybe the 9'' is the only option. Maybe they are racing under more varied conditions. Or they are still experimenting on their set up and a gear change might be needed later in the buildup to stay competitive during the season.
For people like me I've never had a 9'' but plenty of 12 bolts and I don't switch gears alot. So I will stick with what I know as it is less hassle to learn something new. I have enough to do already and would rather leave it to the more daring members of this site!
Maybe the reduced power less of the 12 bolt will help my highway MPG. Just kidding!
11-06-2007, 04:46 AM
#11
My Moser 12 bolt was completely quiet for many, many miles of street use and dyno runs. After I took it to the dragstrip with M/T ET streets, it picked up a considerable amount of noise. My car had a 6 speed in it at the time, and I was launching the car at 4000 rpm. This seems to be a very common problem with both Moser and Strange 12 bolt rears, when used in our torque arm cars. There does not seem to be a gear noise problem when a 12 bolt is used in an older non torque arm equipped car or truck. I have a feeling the torque arm is causing the 12 bolt housing to flex, causing the gear noise. Automatic equipped cars seem to fare better with a 12 bolt, and pricing is pretty equal between the two. Bob
11-08-2007, 12:44 AM
#12
My Moser 12 bolt was completely quiet for many, many miles of street use and dyno runs. After I took it to the dragstrip with M/T ET streets, it picked up a considerable amount of noise. My car had a 6 speed in it at the time, and I was launching the car at 4000 rpm. This seems to be a very common problem with both Moser and Strange 12 bolt rears, when used in our torque arm cars. There does not seem to be a gear noise problem when a 12 bolt is used in an older non torque arm equipped car or truck. I have a feeling the torque arm is causing the 12 bolt housing to flex, causing the gear noise. Automatic equipped cars seem to fare better with a 12 bolt, and pricing is pretty equal between the two. Bob
Just asking.
My 12 bolt doesn't make alot of noise. It was set up professionaly. Every once and awhile I hear a "spooling up" sound while speeding up. No coasting or decel sounds.
See I just don't get how the 9'' doesn't have problems with seperation of the gears under the power. Does the secret lie in the centersection of the 9''?
11-08-2007, 02:09 AM
#13
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Are you saying there is seperation under power of the gearset thus causing unnormal wear --> noise. Or are you saying the old 4 link 12 might not have so much sound because of the rubber bushings isolating the noise?
See I just don't get how the 9'' doesn't have problems with seperation of the gears under the power. Does the secret lie in the centersection of the 9''?
See I just don't get how the 9'' doesn't have problems with seperation of the gears under the power. Does the secret lie in the centersection of the 9''?
Rear loaded housings spread the carrier bearings apart when power is applied. This happends due to when the tire's hook... the tire's tend to pull the wheels forward (and some from the chassis weight drawing down centerline), which then bends the axle tube at the wheel end forward and it toe's the tire's in. When the carrier bearing journels get 'opened' up form this load... the carrier itself looses preload and the gear mesh is effected. That alone can cook a gear set in no time. This is the biggest reason you see braces on the backside of differential housings. The reason for it being done on a 9" is more to combat the toe change than anything else.
The 9" on the other hand isnt effected by this... because the third member is self contained and the axle tubes do not directly effect the carrier and or gear set-what so ever. Also since the 9" utilizes three bearings to support the pinion... there is more mechanical support to combat pinion deflection.
The three bearings are of course, the pinion bearings themselves internal to the pinion bearing support and a 'spigot' bearing on the back of the pinion gear. There are also quite a few aftermarket alloy cases that also use a 'load bolt'. The spigot bearing controls the head of the pinion and pretty much negates deflection to itself and the load bolt combats ring gear deflection and minor case spreading.
These are things that most dont have to worry about due to running street compound tires and that most of the time... you car doesnt hook THAT hard. But, it none-the-less is something to consider and remember when getting into elevated power levels and chassis tuning.
11-08-2007, 04:18 AM
#14
Well... yeah. All rear loaded differentials have this problem... 7.5", 8.5", 8.875", 9.25" and the corporate 10.25". And yes... the bushing material does help to combat noise transfer to the chassis in the case of the torque arm three link.
Rear loaded housings spread the carrier bearings apart when power is applied. This happends due to when the tire's hook... the tire's tend to pull the wheels forward (and some from the chassis weight drawing down centerline), which then bends the axle tube at the wheel end forward and it toe's the tire's in. When the carrier bearing journels get 'opened' up form this load... the carrier itself looses preload and the gear mesh is effected. That alone can cook a gear set in no time. This is the biggest reason you see braces on the backside of differential housings. The reason for it being done on a 9" is more to combat the toe change than anything else.
The 9" on the other hand isnt effected by this... because the third member is self contained and the axle tubes do not directly effect the carrier and or gear set-what so ever. Also since the 9" utilizes three bearings to support the pinion... there is more mechanical support to combat pinion deflection.
The three bearings are of course, the pinion bearings themselves internal to the pinion bearing support and a 'spigot' bearing on the back of the pinion gear. There are also quite a few aftermarket alloy cases that also use a 'load bolt'. The spigot bearing controls the head of the pinion and pretty much negates deflection to itself and the load bolt combats ring gear deflection and minor case spreading.
These are things that most dont have to worry about due to running street compound tires and that most of the time... you car doesnt hook THAT hard. But, it none-the-less is something to consider and remember when getting into elevated power levels and chassis tuning.
Rear loaded housings spread the carrier bearings apart when power is applied. This happends due to when the tire's hook... the tire's tend to pull the wheels forward (and some from the chassis weight drawing down centerline), which then bends the axle tube at the wheel end forward and it toe's the tire's in. When the carrier bearing journels get 'opened' up form this load... the carrier itself looses preload and the gear mesh is effected. That alone can cook a gear set in no time. This is the biggest reason you see braces on the backside of differential housings. The reason for it being done on a 9" is more to combat the toe change than anything else.
The 9" on the other hand isnt effected by this... because the third member is self contained and the axle tubes do not directly effect the carrier and or gear set-what so ever. Also since the 9" utilizes three bearings to support the pinion... there is more mechanical support to combat pinion deflection.
The three bearings are of course, the pinion bearings themselves internal to the pinion bearing support and a 'spigot' bearing on the back of the pinion gear. There are also quite a few aftermarket alloy cases that also use a 'load bolt'. The spigot bearing controls the head of the pinion and pretty much negates deflection to itself and the load bolt combats ring gear deflection and minor case spreading.
These are things that most dont have to worry about due to running street compound tires and that most of the time... you car doesnt hook THAT hard. But, it none-the-less is something to consider and remember when getting into elevated power levels and chassis tuning.
This should be a sticky! Bob
11-08-2007, 07:20 PM
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I like 9" rear ends because you can take them out and put them on the bench to work on. Moreover, you can still find the strong Nodular Iron carriers in the junk yards, so you can have a spare cheap and easy with a different ratio if you like. The Nodular Iron carriers have a large "N" cast into them.
11-12-2007, 01:37 AM
#20
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Here is some food for thought.
When I broke my first 10 bolt it was 1500 miles after I installed a Rossler TH400 RMVB with a 4k stall. I had another 10 bolt with 2.73 gears laying in the backyard so I threw it in. Started leaking at the pinion seal shortly afterword. I did some research and decided I was going to buy an S60, I wanted overkill. While saving my nickels and dimes a Strange 12 bolt came up for sale used, it had 4.10s and a spool and was shortened 2.5 inches on each side. Very close to exactly how I wanted a rear setup. It was a little expensive in my opinion for a used rear at first so I just kept an eye on it. Several weeks later the price had come down to my ballpark figure and I purchased it.
The point I am trying to make with this little story is I love this Strange 12 bolt and do not regret whatsoever having purchased it instead of an S60 or a 9 inch. If you don't plan on making more than 750 horse a 12 bolt will suit you just fine.
I believe the biggest durability factor is in posi units versus spools. I believe this is true no matter what rear end you choose. A spool will be stronger everytime.
When I broke my first 10 bolt it was 1500 miles after I installed a Rossler TH400 RMVB with a 4k stall. I had another 10 bolt with 2.73 gears laying in the backyard so I threw it in. Started leaking at the pinion seal shortly afterword. I did some research and decided I was going to buy an S60, I wanted overkill. While saving my nickels and dimes a Strange 12 bolt came up for sale used, it had 4.10s and a spool and was shortened 2.5 inches on each side. Very close to exactly how I wanted a rear setup. It was a little expensive in my opinion for a used rear at first so I just kept an eye on it. Several weeks later the price had come down to my ballpark figure and I purchased it.
The point I am trying to make with this little story is I love this Strange 12 bolt and do not regret whatsoever having purchased it instead of an S60 or a 9 inch. If you don't plan on making more than 750 horse a 12 bolt will suit you just fine.
I believe the biggest durability factor is in posi units versus spools. I believe this is true no matter what rear end you choose. A spool will be stronger everytime.