The age old question, 12 bolt or 9 inch rear?
 

I am looking to get a new rear for my 98 z28. I am beefing up the power a lot. Looking to run low 10's or possibly high 9's. But i am still keeping it a street use car. I mean i would use it at the drag strip once in a blue moon, but mostly on the street at a lower boost mind you. But would a 12 bolt suit my needs more if i am looking to make it more of a street car? I mean i don't want something to break if i take it the track the few times i may be running it. Also, what is the draw back with not having ABS? And also, since i am keeping it more of a street car, what gears would you guys recommend for street use? I mean more than likely i am not going to be good at launches, but then i do want to sacrifice too much gas either. 4.10s seems like a bad idea if i ever decide to drive long distances. But if i ever race some one on the street, i don't want to be peeling out instead of beating the guy either. I do have BF Drag radials on the rear. And lastly, based on what i wrote, what kind of setup for the rear would you guys suggest? I hear detroit locker, posi, spool. I am not sure what those even do.

I dont think your goals are logical. You wanna go 9's and drive it on the street at a lower boost, okay with that given youre gonna need quite a gear to go into that kind of time unless you are making ALOT more power. If you are thinking of running 9's and are worried about gas mileage I think you need to sit down and learn what it takes go go that kind of time. Sounds to me like you need two cars. One to run to race and one to drive around on the street and get decent mileage.

a 12 bolt or a 9 inch will be fine. I personally would go for a strange S-60, but thats just me.

I would say 9" or Dana 60....

- Justin

another vote for a 9in...you could even have 2 third members...one with street gears and a locker/posi with 3.23's or 3.55's then real steep gears with a spool for the track-4.56's or something...and just swap them out...

we have a 32 inch in diam tire and 4 56 gears in a 12 bolt 2 spped glide and shifting at 6800 going through traps at 7000 car goes in hot weather 9 40s 141 mph think about using one of the richmond gear charts to plot your gearing and a 9 does give you a quick change deal my 2 cents jz

Okay, the dana 60 intrigues me. I thought i saw some one post that you can have 3 or 4 channel ABS on the Dana. is that right? Also, i assume its meant to be a strong rear, or else you wouldn't have mentioned it. I am familiar with some cars that run good times and still get decent gas mileage though. I am not expecting to get 20 miles to the gallon here, but i am not expecting to get 8 either. I mean if you turn the boost down and keep it at a reasonable level, i would think that plays some influence on the fuel economy.

Well, will a turbo, you can have the boost set at 20 psi, and as long as you drive around town with a light foot, you prolly won't ever see boost. Turbos spool when there is a load on the engine. A turbo car at cruise speeds acts like an N/A car most of the time.

There is more to it than that - but that's the general idea.

- Justin

I am happy with my 12 bolt, but if I had it to do over again I would go with a Billingsley 9 inch custom housing with an aluminum center section over anything else.

yeah but how much do one of those run?

http://www.ls1speed.com/shopcar.cfm

Or this one (not an ls1 car same concept my friends old car)

http://www.eiptuning.com/eip/videogt...dpasslarge.mpg

first FWD VW into the 10's getting 22 mpg

LS1Speed's car is nice, but still only has two of the three requirements. With that motor and no OD (even with the 3.42 rear), I'm betting the milage sucks. Which is fine with me. I don't associate F-bodies with mileage, never will....but that is one of the things that redbandit seems to want.

- Justin

12bolts are jsut as strong as 9inch rears. 12bolts also have less internal resistance, leaving more power reaching the wheels :)

I have a 12 bolt for a reason! they use less power then a 9" rear. in the quest to go fast, why handicap your car with something that requires more power to turn if you dont absolutely need it.

I know someone that had a 9" in a 88' camaro that ran 9.30's n/a, and he switched to a moser 12 bolt, and did nothing else to the car, it gained 17hp on a chassis dyno,plus it now goes 9.26. plus i think the 12 bolt is about 20lbs lighter. JR1.

Keep it GM. Go with the 12 Bolt.

dana 60 FTW!! :D

Strange 12 bolt, or S60.

**** it through a 14 bolt with 4.56 gears and say **** the gas milage and beat the balls out of it and hope the motor dont go hahaha i dunno but good luck with it

12 bolt with 9" housing ends.

Forget the Dana. Way too heavy and in almost all cases it's overkill.

a dana 60 for running 9's is overkill?

I have a Moser 12 bolt with 4 11 gears. I don't have boost but I use the juice. My old best was a 10.46 (shooting for 9's in August). I drive the car on the street and the only thing I don't like about the 12-bolt is the whining so I just turn up the stereo. :mrgreen:

i agree. im going that route this fall!

In my opinion, yes. You can run 9's safely on a 12 bolt or 9" rear with no problems at all, tons of guys do it. Guys in the NMCA run 8's on the 8.5" 10 bolt (most notably Kurt Urban last time I saw). The Dana 60 is very heavy and has a lot of rotating mass (9 3/4" ring gear IIRC). Good for offroading but not drag racing.

Your right, kurt did run a 8.5" 10 bolt, but the rear end internals is what makes the rear strong not the housing. JR1.