99WS7

iTrader: (13)

Just curious. Im really trying to narrow down what to get. I've everything from under the sun and really I just want what is best for a semi daily drivin car that will see track time atleast once a month during the season. It needs to be able to handle 575HP to the wheels. I have a M6 if anyone has some advice.

xpndbl3

iTrader: (23)

9" for stick cars

LS1>girlfriend

iTrader: (19)

12 bolt will work, it will be lighter and you wont have to pull the entire center section to check gears or change fluid

99WS7

iTrader: (13)

see thats what Im saying? Why is a 9" better for manuals? Wouldn't a 9'' be easier to change out the gears cause it has a third member or something like that?

xpndbl3

iTrader: (23)

15 pound difference typically. Gear fluid can be changed by drain/fill ports on housing. Furthermore, the 12 bolt will whine typically after a bunch of strip passes with a manual, whereas a 9" won't.

LS1>girlfriend

iTrader: (19)

is that with the aluminum center section? drain holes dont let you get into the housing to wipe away the rest of the shavings, check the gears for out of the ordinary wear. the reason a ring and pinion will whine is because of the way they are setup. mighty mouse was make 995 rwhp and running a moser 12 bolt...thats saying something.

EPP

iTrader: (22)

http://www.exoticperformanceplus.com....html?item=145

Put a 12 bolt into a early Chevelle, Nova, Camaro, etc and you can beat the crap out of it, and not hurt anything. Put one into one of our cars with a torque arm, make a couple 4000 to 5000 dragstrip launches, and I can just about guarantee you'll pick up gear noise. If it is a drag only car, you'll never know or care about the gear noise. Drive your car home from the track, and the noise will drive you nuts. I feel the torque arm stresses the 12 bolt housing, causing distortion. We have never seen this happen with the 9 inch housing.

Exotic Performance Plus strongly recommends the Moser nine inch. This rear is even tougher than the Moser 12 bolt, and the horsepower of the late model F Body cars keeps escalating every year, which requires a very strong rear. With the recent introduction of the 6.2L GM aluminum block and the excellent flowing 6.2 litre heads, the horsepower of these cars is going to just keep climbing at a very fast pace.The nine inch will handle the power, plus we prefer the way the torque arm is bolted to the nine inch in the same way the oem rear-end is attached. (This is the only good thing about the stock 10 bolt...) The Moser 12 bolt uses four short bolts to attach the torque arm, and they have a habit of loosening up, even when loc-tite is used. Why the nine inch is stronger than the 12 bolt. The 9-inch has an internal rear-pinion support that also supports the gear end of the pinion to limit gear deflection under high torque loads. This seems to be the major reason why the 9 inch doesn't start whining after high rpm clutch dumps, when the 12 bolt will pick up noise.The 9-inch locates its pinion gear lower on the ring gear to improve tooth contact, than the 12 bolt does.The 9-inch has a 0.125-inch larger ring-gear diameter and internal pinion support than the 12 bolt does. This is not much of a difference, but it is worth noting. Bob

Speed

iTrader: (33)

9 inch here too. From my research 15lbs is the difference iron vs iron. The aluminum center on a 9 inch makes the rear lighter than iron 12 bolt. Just regurgitating what I've read. Honestly I didn't give a ****. I'm running a 9 inch truetrac in my daily driven strip and roadcourse M6 SS and I love it. In a past 9inch, it survived 6k clutch drops on a 550hp car that turned a stock driveshaft into a spear. I haven't run a 12 bolt but after two 9 inches now, I know they work and that's all I will ever run.

Drain plug makes it a snap to change fluid and the 3rd member isn't really THAT hard to remove.

1fastz28nx

iTrader: (18)

99WS7

iTrader: (13)

word...

LS1>girlfriend

iTrader: (19)

you dont think its easier to take out 12 bolts than to take out how ever many bolts there are (also makes it difficult getting the top bolts) pulling down a 50ish pound center section on your chest and somehow getting it out from underneath the car? oh ya and unbolting the ds. ive done it befor...i choose unbolting the cover without jacking the car up . my 12bolt makes no more noise than 9 inches ive heard and for street and some strip driving why do you need the extra pita?

i know you 9" guys are biased but for street and some strip driving its more work than it needs to be.

onebad82z

iTrader: (1)

Whew, glad I have a non "typical" 12 bolt in my M6 car.No whining here!

Sharpe

iTrader: (7)

This thread has some really good real-world info at the beginning.

How about power drain? Doesn't a 9 inch eat a lot more power than a 12 bolt?

chicane

Not at all correct.

The difference is 30 pounds (but can be more or less depending on what you are comparing.) And a 12 bolt wont whine after a couple of passes because it being used in a manual chassis with a bunch of 1/4 mile passes. It makes noise because it wasnt set-up correctly from the get-go.

See number 4 below.



Lets get rid of some of the mis-conceptions.

1. The newer 12 bolt housings are from the KTRE molds. The center section is made of ductile iron and they use 3.00" dia 4130 tubes. The main cap webbing has been reinforced, they use 1/2" fastners and the main caps are larger to combat cap distortion. The main caps themsleves are constructed of nodular 65-45-12 iron material.

2. The housing ends are not Ford, (although you can special order it with various other housing ends.) The housing ends are GM midsize, offered to fit 58503, 504 or 505 in a sealed bearing cartridge or a 58506 tapered roller bearing. The housings also use either 3.062 or 3.250" bore components.

3. A 35 spline axle in a 12 bolt is a no-no... unless you use a Mark Williams spool with a specific 'high pressure angle'. Not to mention that when you use an axle larger than a 30 or a 33 spline, the carrier journels become so thin that even normal street will snap the bearing journels clean off the carrier housing.

4. The difference in pinion height is 0.75", which equates to about 3.5% in efficiency. This higher pinion location in the 12-bolt results in lower gear lubricant temperature, improved fuel economy, and best of all, more power delivered to the ground.

5. A "third member" design differential housing is stronger in many aspects. The most obvious is that it allows the tubes to flex without effecting the carrier bearing pre-load, which in effect opens up the pinion to ring gear mesh. You can even use a 12 bolt third member... in a 9" housing to get the best of both worlds.

6. Ratio availability goes to Ford, hands down. As does the simplicity of changing the center section with a different differential device and/or gear ratio. Although, it take the same amount of time to swap gears in a 9" or a 12 bolt... just having a pre assembled third member makes it a litter eaiser and a-lot less messy.

7. The axle hop is related to a combination of the IC angle, from the pinion angle difference, and the hieght of the axle tube above the spring. A taller spring perch yields a longer torque arm on the spring itself.

Some housing have drain plugs in them, some dont. You can still siphon the fluid from the fill port on the center section.

All in all... its a wash. For a heavy car that can actually hook up a-lot of power... a 9" has its advantages. In a moderate weight car that is used on street and track/road course... either. In a lighter chassis with a firmer suspension... a 12 bolt. You can however spend more on a 9" than a 12 bolt in a heartbeat.

One common problem around here... is Moser and Strange. I have never heard more complaining about ger noise and set-up issues in my life... and all of them are associated to differentials being built from Moser or Strange.

Do your home work. There are more people that build differentials and that have way more experience than Moser.

EPP

iTrader: (22)

The Moser 12 bolt in my own '99 Z28 was dead quiet until some 4000 rpm dragstrip launches. We have had this same problem with our customer's cars as well. It has not happened to the Moser nine inch rears that we have installed. Bob

99WS7

iTrader: (13)

good info chicane.

Enforcerws6

iTrader: (1)

Did you set the rear up yourself or just take it new and put it in the car. Everyone says that both these companies do a poor job of setting them up and thats how they build them so fast. If no one checked to make sure everything was set up PERFECT its going to start making noise later. Just my two cents but then again this is all comming from what I have read not from experience. But I would have to be real certain a 9" is way better to put one in my car. I think that the rear is the only ford has ever done right but its still a ford part.

Gangreen

iTrader: (2)

Here is the skinny on this:
1. even though it is made for ford, the 9" is virtually indestructable. Even though they a heavier, they are known for durability.
2. The 12 bolts are still GM (unless Moser or Strange has found a way to fortify them) Gm rears are not strong at all and buckle under pressure. Soooooo, for the same amount of money as a Ford 9", you can get a rear that is destined to break......

badmfkr

iTrader: (4)

fluid can be sucked out thought the top speed sensor hole on a 9"

INMY01TA

iTrader: (1)

My Strange 12 bolt was dead quiet till the 5,500rpm dumps.