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.

 

Lots of people want a 9-sec. street car, few people have one. A car with enough power to run 9's will not hook up with street tires, or 10" DR's for that matter when on an unprepped surface. So you certainly don't need a 9". The amount of available grip will be the "fuse" so to speak and allow you to use the more efficient, less bulky 12-bolt. Another advantage of the 12-bolt is the availability of the Eaton posi, which AFAIK is NA for a 9". You do NOT want a spool on a car that is primarily driven on the street. If someone wants to dispute this, I would say they are dead wrong. A locker is marginally more acceptable, but I wouldn't have one for a street car under any circumstances.

IF you want a bullet proof rear end for a heavy car with sticky tires capable of running 9's you should get a 9" with a spool. But it will not be streetable, IMHO. Also keep in mind that not all 9" are created equal. Ditto for 12-bolts. There are a lot of choices for the 9". Just 'cause it's a 9" doesn't mean it will be super strong. A strong 3rd member with a good nodular iron case, high quality gears, differential etc. is going to run at least $1,500+. And, of course, you still need the housing, axles, etc. which is going to run close to $1,000. A 12-bolt will be a little cheaper, but not much. Then, you need a driveshaft for another $300+, a tranny up to the task with appropriate converter/clutch, upgraded torque arm, etc., and so it goes. Do you really want a 9-second street car? Can you afford one?

Rich

 

How 'bout Strange's new Dana 60 F-body rear? Super strong, 3- or 4-channel ABS, efficient, similar price as the 12-bolt and 9". I know that doesn't really answer your question.

A spool is for race-only cars - the left and right rear axles are essentially locked together when you have a spool, so turing corners on the street would be a pain. A locker is a diff that will lock together when needed for traction, and unlock when needed for cornering... so they're streetable, but they're usually pretty harsh when they lock/unlock. My Blazer has a factory-equipped Eaton locker rear - it's clunky at times, but perfectly streetable. I find that it's locking/unlocking in certain situations is a little weird, and might cause some spooky handling in a high-HP car - flooring the throttle mid-turn means it's a crapshoot as to whether you get 1 wheel spinning or 2. A posi is short for Positraction, which is GM-speak for a limited-slip differential. Posi's are the most comfortable for the street (which is why they came in our cars from the factory) but don't have nearly the locking power of the other 2.

So as you go from pure race car to pure street car, you go spool > locker > posi. It's up to you where you firgure your car fits into that.

 

Well said. A locker can be tolerable for easy street driving if you can tolerate the "clunk" but I wouldn't try any fast cornering with one due to it being somewhat unpredictable, as you pointed out. The way to get a solid rear axle car to corner quickly but tidily is to brake in a straight line and enter the corner under a little power, as you go through the apex you squeeze on the throttle. What you don't want to happen is to have the locker decide to lock or unlock during this process as this can upset the car and lead to loss of control at worst, or a very unsettled feeling at least.

Rich

 

I disagree. I ran a spool for several years back in the 80's and my '69 Camaro has had a spool for the last 6 years. The only time you can tell it has one is when going real slow in a parking lot making sharp turns. You can hear the inside tire slipping on the pavement.

Obviously, you would not use one if you intend on autocrossing or pulling max g's through a corner. A spool is designed for drag racing but it can be used on the street just fine.

 

So is the Dana 60 a better choice than the 12 bolt and 9 inch then? I mean is it a good street friendly choice? I mean if not, then you guys gave me the answer i needed. a 12 bolt with posi. But yes, i can afford it. I currently have the money for the engine, and tranny and turbo charger. All that is left is the rear, the brakes, a few
minor suspension mods, and safety mods. And what about 3 or 5 channel ABS? Which would i need?

Also, can you guys go more into the tire thing. Even if a 10 in drag radial won't hook on a street surface, then what do i use at that point? I mean what do most people use at that point? I am guessing that if i drive the car long distances, i can just change back to the current 18 in tires i have, but most of the time just use a smaller tire, right?

 

So is the Dana 60 a better choice than the 12 bolt and 9 inch then? I mean is it a good street friendly choice? I mean if not, then you guys gave me the answer i needed. a 12 bolt with posi. But yes, i can afford it. I currently have the money for the engine, and tranny and turbo charger. All that is left is the rear, the brakes, a few
minor suspension mods, and safety mods. And what about 3 or 5 channel ABS? Which would i need?

Also, can you guys go more into the tire thing. Even if a 10 in drag radial won't hook on a street surface, then what do i use at that point? I mean what do most people use at that point? I am guessing that if i drive the car long distances, i can just change back to the current 18 in tires i have, but most of the time just use a smaller tire, right?

 

The point I was trying to make is that in the lower gears you can't just "point and shoot" a car this powerful with the tires available for street use. Even a DR on a typical street just isn't sticky enough to use WOT in the lower gears. this will serve to protect the drivetrain, to a point. It's hard launches out of the hole that will break driveline parts.

Rich

 

If your car has ABS and no traction control, you need a 3-channel system. That means the rear axle assembly has a single ABS sensor on the top of the differential housing, and a reluctor wheel on the carrier. If your car has ABS and traction control, you need a 4-channel system. That means the rear axle assembly has a sensor on each end of the axle housing and a reluctor gear pressed on each axle, behind the hub.

If you have a 5-channel system, you're piloting the Starship Enterprise.