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!

 

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

 

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).

 

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.

 

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?

 

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

 

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?