How easy to launch car with non-posi rear?
- Thread starter 86SS86LS
- Start date
If your ride is really making 350 to the ground then good luck with a 12 sec pass......spin,spin spin, you really need to get a posi from my exsperience there is no launching with a one legger. You not going to be able to launch and if you did get one tire to stick the car would not come out straight.
If you want to go racing and get a decent pass get a posi
If you want to go racing and get a decent pass get a posi
challengermike
Member
- Joined
- Nov 14, 2005
I would spend the money on a posi carrier for what ever you rear diff is now.Even if its a 7.5.You wont hook at all with an open diff.
Its very hard to do a burnout with an open rear. Thats why they are somewhat critical. The posi does little for traction after the car is launched under power. You need to equalize the force on both sides of the rear so that the tires have equal traction. Traction is equal till one of the tires slips. Preventing the less loaded tire from slipping will maintain traction. An air bag in the right side is a good start. Ballast over the right rear will help also. I cant believe people actually think a few clutches will actually prevent the tires from spinning. It sure as hell wont. You can easily make a posi rear slip with a breaker bar if one side of the car is on the ground and the other is jacked up. Our engines are supplying way more torque then we could ever apply by hand that is then multiplied through the converter, trans, and rear gear before it hits the tires. Nothing to do with a posi.
challengermike
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- Nov 14, 2005
I agree that a posi is not as good as a spool,but 2 tires trying to hook is better than 1.I would guess if you had slicks or drag radials on a car that didnt have alot of torque you might get away with an open rear.As for the posi slipping,they seem to hold pretty good.Sometimes you see them slip at the track were its sticky.I would say a posi does help traction alot.Take a car and that comes with an open rear and put a posi carrier in it,it will usually spin alot less than it did before.
Like i said once already. With an open rear both tires are trying to hook until one spins. Equalizing the force on both sides of the car will hook just as well as a posi. Problem is you wont be able to do a burnout effectively with an open rear. Yes limited slip rears slip all the time at the track. Luckily the track prep is so good that the tires hold and dont spin. Would be the same as an open rear. If they spin they need suspension work. A spool is a totally different thing than a posi and not used for the same purpose as a posi.
My first turbo T was an 87 Limited with an open rear, non G80. I put an air bag in the right rear spring and pumped it up to 20 psi. Every now and again I was able to get both wheels to spin when doing a burn out.
You have to launch a little softer than with a posi but back in 1988 I got that car to run 13.3s at 101 on 235/60R15 street tires. The MPH was low because I was getting KR upstairs most likely due to a weak fuel pump. Mods were a K&N cone filter, KB chip, no cat.
With the exception of Roy Rauch, Greg Voss (I think that was his name....he had a 87 GN and a tan GS), Eric Schertz and Lazaris (screen name on this board) ......guys who always ran M&Hs and race gas (Eric sometimes ran race gas), I had the fastest TR on Hempstead Tpke in Levittown NY. And there were A LOT of TRs on the Pike back in 88 lol.
So it's possible to go pretty fast w/o a posi. The air bag pumped up to 20 psi helped.
Those were the good old days.
You have to launch a little softer than with a posi but back in 1988 I got that car to run 13.3s at 101 on 235/60R15 street tires. The MPH was low because I was getting KR upstairs most likely due to a weak fuel pump. Mods were a K&N cone filter, KB chip, no cat.
With the exception of Roy Rauch, Greg Voss (I think that was his name....he had a 87 GN and a tan GS), Eric Schertz and Lazaris (screen name on this board) ......guys who always ran M&Hs and race gas (Eric sometimes ran race gas), I had the fastest TR on Hempstead Tpke in Levittown NY. And there were A LOT of TRs on the Pike back in 88 lol.
So it's possible to go pretty fast w/o a posi. The air bag pumped up to 20 psi helped.
Those were the good old days.
Ballast helps too
It would be a very easy and your best option. Shims rarely need to be changed when doing so. Just keep them on the same sides they came out of. Even the Eaton and Auburn ls units seem to go in without the need to re- shim in most instances. Id throw a set of fresh clutches in the posi before installing it. Probably take an inexperienced person 2 hrs to do the change. Ring gear bolts are left threaded. So dont tighten them and break them off in error
.challengermike
Member
- Joined
- Nov 14, 2005
Its very easy to install the carrier.Just pull the rear cover.Then you should mark the caps,i usually put 1 dot on the left and 2 dots on the right cap.Also when i put the dots on i usually put the dots on the top of the caps so you know which side goes up.You will need to pull off the wheels and brake drums.Now pull the bolt out that hold the spider gear pin in and pull the bolt and then the pin out of the carrier.Give the axles a push in and the c clips will fall out and allow you to pull the axles out.Then pull the caps off and then pry the carrier out.Make sure you watch the shims on the sides of the carrier(mark them if you can so you know which side was which.Then unbolt your old ring gear and bolt it on the new carrier.Now put some greese on the side shims and stick them in the case where they were.Now slide the carrier back in,you will have to hit it in with a dead blow hammer or a brass one.Just make sure you hit one side then the other.You want it to go in straight,also grab the joke and make sure its meshing with pinion correctly.When its in torque the caps to about 60 foot pounds.Now pull the pin out of the new carrier and slide the axles back in.This time you will want to put the clip in and push the axle back outwards untill it stops.When both axles are in you can reinstall the pin and tighten the bolt.Put your drums and wheels back on,Relinstall the cover,fill it up and and your done.It sounds like alot of work but it really easy and goes fast.I would say it might take about 1 hour to do.
I really don't know what type of mechanical experience you have but I did mine and it was fairly easy. I went from the pegleg to and eaton and it may a big difference to me.It would be a very easy and your best option. Shims rarely need to be changed when doing so. Just keep them on the same sides they came out of. Even the Eaton and Auburn ls units seem to go in without the need to re- shim in most instances. Id throw a set of fresh clutches in the posi before installing it. Probably take an inexperienced person 2 hrs to do the change. Ring gear bolts are left threaded. So dont tighten them and break them off in error
Turbo6Smackdown
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- Dec 31, 2005
Sorry this is soo old but I need some info from ya. It's hard to do a burnout with an open rear? How do you figure that? You said that when one tire starts to spin, it gives more torque to it. How would that equal a harder burn out? I've had an open in every car I owned, and it was VERY easy to do a burnout. I'm missing something. My posi rear end is a little harder to do a burn out in.
I said once one tire loses traction all the torque will go to the tire that slipped. None to the other. Therefore you wind up spinning one tire. Therefore proper burnout is not easy. One hot tire one cold. With a limited slip there isn't enough brake away torque to slip either axle during a water burnout because the clutches are loaded by the spring. So both wheels will have even torque and both will spin at the same rpm. Once both tires are properly heated and the suspension loaded the limited slip does about nothing to prevent further wheelsman on launch. Proper suspension setup does everything.
BPE2013@hotmail.com
Turbo6Smackdown
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- Dec 31, 2005
Ahh a PROPER burn out. Ok then, that makes sense. I was very confused lol. So going off of that, if one slips, and it gives even more torque to it, then tell me how a limited slip still does nothing on a proper launch. There's a reason performance cars got posi, while their non performance counter parts didn't. It must help traction.
Go grab a breaker bar and jack the car so one rear wheel is off the ground and get on a lug and turn clockwise. You will see that the limited slip will give. The same way it gives in a turn. Think about how much torque it took to make it slip. 100 ft lbs? Notice the other tire didn't slip. The engine has 500 ft lbs of tq on a mildly modified engine. Then it goes through the converter which will multiply tq, then through first in the trans (2.76:1, 200-4R) then multiplied times the axle ratio. The torque at the center of the axle is 4719 ft lbs not including anything the converter adds to the mix which at certain ranges is doubling the engines output. it took 100 ft lbs to make the limited slip slip. If the tires don't slip the diff could be open and traction is still equal because the tq to each wheel remains equal till one slips.
BPE2013@hotmail.com
Turbo6Smackdown
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- Dec 31, 2005
It remains equal till one wheel slips? Unless absolutely EVERYthing was perfect. Plumb and square roads, with zero rocks, no road crown, no water, precisely the same PSI in each tire, with equal tire wear etc. etc. which we all know never happens. Basically 99.9% of the time one wheel will always have a little more traction than the other. Sooo.... if this defeats the entire purpose of a posi, why was it ever invented? I, like most people think, that once you hit it hard, it shocks the clutches into grabbing, (something you don't do on turns, so the slip test doesn't count, because that's not how it was intended to be operated in the first place) thus locking both wheels together. If it didn't do this, then you're saying that an open and a posi are absolutely identical. And they can't be. What's the point of a diff that doesn't lock wheels together under torque?
Then why when you see a guy floor it in an open diff car, one wheel spins forever, equaling zero traction, and when the posi cars floor it, the car hooks up and goes forward? If the clutches are doing absolutely nothing for the wheel spin at launch, then it's behaving exactly like an open diff: no control of wheelspin at launch. Which doesn't make any sense. So if they don't control wheel spin at launch, how would you ever know your clutches are worn?
Then why when you see a guy floor it in an open diff car, one wheel spins forever, equaling zero traction, and when the posi cars floor it, the car hooks up and goes forward? If the clutches are doing absolutely nothing for the wheel spin at launch, then it's behaving exactly like an open diff: no control of wheelspin at launch. Which doesn't make any sense. So if they don't control wheel spin at launch, how would you ever know your clutches are worn?
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