Gears & Axles - question on a 9" or should i go 12 bolt?

im getting close to getting a stronger rear for my car, and now i really have to think of my choices. originally i was thinking 12 bolt but recently im leaning more toward the 9" im most likely going with moser. on a 9" can i retain my ABS (i do not have tcs)? My car is pretty much daily driven, all mods are in sig along with the power i make. I dont plan on doing to much performance stuff for a while besides a 90/90 setup after i finish my drivetrain stuff. The car will see the track, and if i get tired of the power an want more then im definitly gunna be sqweezing. So what you guys/gals think should i stick with a 12 bolt? or should i go with the bulletproof option the 9"? one last thing if i cannot retain my abs that will bring me back towards the 12 bolt, because im trying to maintain the somewhat easy driveabilty factor alive. Thanks guys

-Ryan

you wont be able to keep your abs.... but who needs it :engarde: the 9 inch and 12 blot fight has been goin on forever and if your search there is tons of info on each. I just ordered my 9inch and i was in the same boat as you but i fig if i am goin to do it do it right the first time and i wont have to worry about breakin it..... and screw abs who needs it :)

You know the "12-bolt" has an 8.875" R.G. think about that for a minute.

Now haven't you seen some heavy ass A-body ie.. Chevelle or Buick GS/ GSX with the stock rear take a beating and live? I know I have.

I think with all these complaints the aftermarket housings must be suffering quality control problems.

If your breaking the diff.. well then, maybe you might just have a race car on you hands and you need a spool.
A properly set-up 12-bolt can handle a lot more than you think.

I just installed a Moser 9" from Driveline Solutions in my car and have been very happy with it. My car was already setup for 4 channel so I didn't have to worry about losing my ABS. I wasn't worried about losing a little more power with the 9" over the 12 bolt because I like knowing that I probably won't have to rebuild this 9" rear end for a while. The 9" is stronger than the 12 bolt and that's why I chose it. It seems like most of the problems with Moser 12 bolts is that they are not setup properly by the people at Moser. I believe the parts that Moser uses are good for the most part though. I'd recommend buying a Moser 12 bolt from Driveline Solutions. That way you can keep your ABS, and know that the 12 bolt was setup right.

If you had an A4 I'd say go with the 12 bolt. But with an M6 get the 9".

depends on if you ever want it to break.. a 9" with a locker and 33-35 spline axles.. and you'll never break it no matter what ya throw at it.. most likely atleast.. and i've heard many cases with 12 bolts starting to whine after a few hard launches.. i ehard they are just set up wrong from moser though..

I've heard of 12 bolts breaking more often than 9" rears too.. but the 12 bolt is lighter and you'll be quicker with less weight.. I wish i had a 12 bolt for weight reasons.. but the 9" i never have to worry about!
good luck!

We've installed many Moser 12 bolts and haven't had any big problems with them. I have a lot of runs on my Moser 12 bolt and I'm at 540 rwhp on my Mustang Chassis Dyno, which would be 40 to 50rwhp on a Dynojet dyno. I've come out anywhere from 4000 rpm all the way up to 6200 rpm while experimenting with my launches. Bob

We've installed many Moser 12 bolts and haven't had any big problems with them. I have a lot of runs on my Moser 12 bolt and I'm at 540 rwhp on my Mustang Chassis Dyno, which would be 40 to 50rwhp on a Dynojet dyno. I've come out anywhere from 4000 rpm all the way up to 6200 rpm while experimenting with my launches. Bob
Is that with a stick or auto?

Stick. Bob

If you had an A4 I'd say go with the 12 bolt. But with an M6 get the 9".


I 2nd that. :)

9'' Will Hold More Power If You Want Something To Withstand Big Power On Launch I Would Say 9'' If You Dont Want To Make Over 600 Hp 12'' Is Not That Bad But Do It Once Do It Right

you wont be able to keep your abs.... but who needs it

Yes you can keep it. It takes a little work on your part. I've posted about how to do it several times so i'm not going to take the time to do it again. A search will land you the info. :)

Lets just say... U answered it yourself. I know MANY guys run the 9" on the street but its drive-a-bility is far less efficent than the 12bolt. So I'd say go with the 12bolt... Thats what I am going to be doing... Goodluck and let us know what your going to go with!

Id say go with the 9in those gears are cake to change.

I got a Moser 9"'s lol 4.10's detroit and 35 spline axles kept both abs/ASR too. I think that was one of the better mods I have done to the car. Too bad I burnt my clutch up on the first and last run that I did in the states w/ that rear end. I still ran a 12.79@110 though compared to my stock set up that gave me 12.9-13.0's quite frequently. I dont think weight should never be an issue compared to durability. One thing for sure about the 9" is that I dont have enough money to even break that thing. I don't doubt 12's are strong but if the gears break in a 12bolt you will have to install new gears under the car or pull the whole rear out. I can just pull the 3rd out and work it on the bench.Which a 9 is easy ass hell to set up. BTW double check your set up from Moser I checked mine out and I needed to tweak some shit. Either way you will be fine. 10 bolts suck well late model 10 bolts do so a 12bolt or a 9 will definatly get you there and back. Oh with the 9 you can make home made spanner wrenches to set the gears cheap too.

damn guys thanks for all the help, im still on the fence on what to do...but ill figure it out...also the only rear company i know of is moser, strange and currie. what are some other ones? what is best? i noticed every1 saying that the moser stuff comes somewhat faulty and takes some tweaking to fix, how big of a problem is that? what is wrong from them? thanks guys/gals
-Ryan

damn guys thanks for all the help, im still on the fence on what to do...but ill figure it out...also the only rear company i know of is moser, strange and currie. what are some other ones? what is best? i noticed every1 saying that the moser stuff comes somewhat faulty and takes some tweaking to fix, how big of a problem is that? what is wrong from them? thanks guys/gals
-Ryan
Moser, Strange and Currie to a lesser extent, are the main ones in the F-body world. There is one more than can make you just about $$$ anything $$$ you want and it doesn't have to be in their catalog.

markwilliams.com

9" all the way

I ran a 9" with a spool every day on the street in my camaro.

I've run my Moser 12 bolt 33 spline TrueTrac with 3.73's 30 some odd times this year and haven't noticed ANY increased gear noise or any gear noise for that matter. Sticky tires with a full bolt on car and a cam launching at 5500-6500 RPM. If there were going to be any problems at my level they would have surfaced by now.

damn guys thanks for all the help, im still on the fence on what to do...but ill figure it out...also the only rear company i know of is moser, strange and currie. what are some other ones? what is best? i noticed every1 saying that the moser stuff comes somewhat faulty and takes some tweaking to fix, how big of a problem is that? what is wrong from them? thanks guys/gals
-Ryan
Lack of giving a shit or quality control whatever you want to call it. Is probably what is wrong with Moser. Maybe the demand to too high for them so they slap shit together. Even if the parts came from someone else I would go ahead and check it first. Since its out of the car it would be easier and give you that piece of mind.

I put it this way. Ive seen the spider gears blow out of the TA cover for the moser 12 bolt. My buddie went to a spool after that. I myself went with the Moser 9' and 35 splines and ditch the ABS 3 channel car. Leave the line at 6250 to 6400 on my m6 with 4.11's racecut and a spec 3f cutting 1.57 sixtys and the rear end doesnt break a sweat.

I too have the Moser 9" in a Daily Driven 2002 SS A4(Auto) with 3.70 "Race Cut" gears.
This has got to be the BEST MOD I've done yet. The Priciest too.
I've run at No Problem Raceway often before I took the SS down for some more MODZ.
On a Slipping Tranny with a Vig.3200 Stall I was still cutting 1.58-60fts. It's an Excellent
Rearend and I've also kept my ABS and Traction Control. I would recommend that you
have the differential inspected to make sure that it's set up properly.
One of the Selling Features for me with the 9" was the fact that you have several
more gear selections to choose from. With an A4 that's important.

Knowing the Reputation that "No Problem Raceway" has (The Track That Bites Back)
I've seen several 12-Bolts lose their internals.....Zero 9"s

Also, If you get the 9" make sure you follow the Break In Procedure!

9" all the way

I ran a 9" with a spool every day on the street in my camaro.

How was that thing on the street? Could you still bomb around on-ramps and such? I'm setting my car up to be a street killer. Full road course suspension, revalved for the street.

Going to go with a Billingsley Racing FAB 9" possibly with a spool. Need to know if its doable, as I've never run a spool before!

OK I think I am getting it: for 600RWHP and RWTQ go with the Moser "9" but less than 550HP go with the 12? Well the 9 is cheaper and stronger, at least on Speed Inc., I'll just get the 9 unless I read research that I shouldn't.

You'll only have to purchase it ONCE!
Wise Choice.
Now you just have to decide which gear setup you need.
Way more choices than the 12 Bolt. (This was the MAIN selling point for me)

hghghggh

How was that thing on the street? Could you still bomb around on-ramps and such? I'm setting my car up to be a street killer. Full road course suspension, revalved for the street.

Going to go with a Billingsley Racing FAB 9" possibly with a spool. Need to know if its doable, as I've never run a spool before!



If your wanting to road course/ auto cross a spool is not for you because it sucks at taking corners. One thing about the spool though, when you nail it you will go pretty much in a straight line. A posi wont even come close to that.

In my opinion, the spool on the street wasnt all that bad, but then again this is someone that daily drove a trex 244/249 109.4lsa with spool, lanes dumps, bogarts, in a stalled auto. The chriping really depends on how stiff the sidewalls on your tires are. Best advice Ill give you is the advice that was given to me, find someone with a spool and see if you can handle it or not.

9", Detroit, 35's. End of discussion ;)

Like DMNSPD stated a 9" with a truetrac is great.

BTW you could give up a little strength for less rotational mass by going with a 31 spline axle instead of a 35.

9 inch all day long. If you end up with a 12 bolt go with the strange unit because of the TQ arm mounting situation with the moser.

Okay, what if you know you are never going to have more mods than heads/cam? My Camaro will never be faster than an 11.50 car because I do want to race it but I don't want to put a roll bar in it. I'd want it to take repeated 5500 rpm dumps off a 2-step reliably because I don't have a tow rig and have to be able to drive the car home.

Driveability is a HUGE concern for me since the car isn't raced regularly. I was thinking either a 33 spline 12 bolt or a 31 spline 9 inch with a TruTrac. I want to keep as much of my horsepower as I can since I won't be putting out much power (>425 rwhp).

Driveability is a HUGE concern for me since the car isn't raced regularly. I was thinking either a 33 spline 12 bolt or a 31 spline 9 inch with a TruTrac. I want to keep as much of my horsepower as I can since I won't be putting out much power (>425 rwhp).

I think the 9 inch is the better option and I believe that is what I will go with. My car is a lot like yours, street driven, no tow rig and not raced all the time. So I'd rather go with a beefy rearend that won't break so I can drive it home. Scott(@ DLS) recommended 9inch, trutrac 31spline 4.11 gear for me. Even if you do lose some power with the new rearend just spray it, a little. :devil:

Yeah, Tom, the more I read about all the 12 bolt failures the more I think I'm going to go with a 31 spline 9" from Scott except I think I'm going with a 3.90 gear.

"9 inch all day long. If you end up with a 12 bolt go with the strange unit because of the TQ arm mounting situation with the moser."

So the 9" moser doesn't have a tq arm issue, but the 12-bolt from moser does? Or buy a strange unit for both sizes?

Yes you can keep it. It takes a little work on your part. I've posted about how to do it several times so i'm not going to take the time to do it again. A search will land you the info. :)

:nod: Also, you can build a 9" lighter than a 12 bolt (almost as light as a 10 bolt, even!), but it will cost BIG $$. Some other reasons for a 9" over a 12 bolt (besides strength) would be greater ratio choices and as said earlier, ease of changing/setting up those available ring & pinions.

9" and detroit truetrac

Yeah, Tom, the more I read about all the 12 bolt failures the more I think I'm going to go with a 31 spline 9" from Scott except I think I'm going with a 3.90 gear.


Watch out with that 3.90 they make a lot of noise.

Watch out with that 3.90 they make a lot of noise.

Why does a 3.90 make a lot of noise? Doesn't noise have to do with how the gear is cut, set up correctly or not, and how it's broken in? I ask because I just ordered 3.89 gears for my 9 inch.

I saw somewhere in this thread about not keeping ABS with the nine inch but you can keep it no problem, you just have to have the axles come with the exciter rings installed or get them machine to accept them and then reuse the sensors.

I have hear mixed reviews, alot of mustang guys complain about the noise, you know this thread is like 3 years old?

^^ nah, it's only a couple of hours old now :)

I looked into those gears a little more, and it seems like its the motive 3.90 that are noisy, even when professionally installed.

I looked into those gears a little more, and it seems like its the motive 3.90 that are noisy, even when professionally installed.

hmm I did order Motive but think they're 3.89 if that makes any difference. I thought Motive gears were supposed to be more quiet than most of the rest. I guess I'll see after they are professionally installed. Does the rear have to be broken in if only the gears are being replaced? The Eaton truetrack is the same just getting different gears and axles too actually.

maybe thats why its a 3.89 and not a 3.90

3.70 gears are almost always quieter than the 3.89 gears in a nine inch, it doesn't seem to matter who the manufacturer is. Bob

9'' Will Hold More Power If You Want Something To Withstand Big Power On Launch I Would Say 9'' If You Dont Want To Make Over 600 Hp 12'' Is Not That Bad But Do It Once Do It Right

I will be going with a 9" when mine goes.

9"...... :cheers:
Only way to go when you're laying down some serious Power!

this thread is seriously like 4 years old. i have gone 12 bolt because I just cruise my car.

Well considering I just blew my 12 bolt to pieces, I say 9" for an M6, auto's are easy on parts...

destroyed the pinion, ring gear, diff, and a bearing cap, and I have an aluminum cover w/preload.

I just built a narrowed 9" for not that much money using some really great stuff moser alum case, Strange 35 spline axles, spool, once it's assembled, and painted I'll post some pics...

GO WITH 9. I have a 12-bolt and it makes so much noise I cant listen to the radio. Moser told my installer to go fuck off when we tride to explain to them something was wrong with the unit.

I HATE MOSER 12-BOLT. In Fact I'll NEVER PURCHASE FROM MOSER EVER AGAIN and I HOPE YOU DON'T ETHER!

Screw a 9". I'm going with an S60. The weight difference is negligable and you gain the ET difference back by having a rear with the hypoid offset closer to center.

Screw a 9". I'm going with an S60. The weight difference is negligable and you gain the ET difference back by having a rear with the hypoid offset closer to center.

FTR. You are also losing SOME small amount of power due to the more massive ring & pinion.

im installing my moser 9 inch right now and yes there is some tweaking , my uni panharde bar is adjusted all the way out and was 8th inch off the hole so i had to put a reamer to the hole but most people dont have a $260 reamer laying around , im an iron worker so it helped , and my stock rear sway bar is hitting the back of the mount for the torque arm , but all in all its a beafy rear and its good to do some work your self but for the price we shouldnt have to do anyting but bolt it up and fill it up , but as companies get bigger and the mass produce stuff , it tends to get sloppy , not saying that about anyones business but you get the point