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Discussion Starter · #1 ·
So I have decided to do a one piece drive shaft and a limited slip differential for my next mods. I am pretty set on the aluminum drive shaft.

I am currently running a 3.07 open differential per my build sheet. Most of the time it spins both tires but on occasion I get a one spin wonder. Like yesterday I left a stop sign beside a camaro on a side road and it spun the right tire for 30 yards.

This is my thoughts, a 3.09 limited slip and a 4" aluminum from The Driveshaft Shop. Thanks Ry. Another guy here in town says a 3.73 but I am Not really looking for a lower end. I'm pretty happy with the low end as is. Just need to wear out the Michelin's and get some rubber down on the road.

I would appreciate any thoughts the rest of you have on my swap. Thanks ahead of time.
 
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I don't think ZF made a 3.73, only Getrag.
 
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Make sure to get a differential brace to bolt on to your 3.09 LSD. I don't have the one-piece driveshaft yet (it's on my list of mods to still do) but I do have the 3.09 LSD with the diff brace. IMO, the diff brace is worth the investment to stabilize and protect your driveline.

I've heard that a 3.70-ish gear ratio in the A8s would have the car in 2nd gear at 4 mph or something like that. Verify that with other, more knowledgeable Z members but that's what I've heard. Best of luck with your upgrades. Dave :)
 

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As far as the wheel spin, what kind of tires you got on the back?
 
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This is my thoughts, a 3.09 limited slip and a 4" aluminum from The Driveshaft Shop.

I would appreciate any thoughts the rest of you have on my swap. Thanks ahead of time.
That 3.09 will be great for your A8 transmission very close to the 3.07 you have now just sending the power to both rear wheels. The 4" Aluminum driveshaft has you covered past 1,000HP and is very little drive line resistance, meaning you're spinning tires now, will get worse.

But you can get better tire rubber composition somewhere around the Treadwear 200 or lower, and get the off the line traction you want and still get some descent mileage out of the tires.

Treadwear number goes hand in hand to tire longevity, many want grip but also want long tire life, and I am sorry it is one or the other, you cannot have both in the same tire.

The first solution most try is wider and wider rear tires which add more weight to the car, and if the rubber composition is too high it still spins them like buttered donuts. I went from wider down to a 275 but went with the 275/40/20 Mickey Thompson ET Street S/S which have a rubber composition of 000, and grip like you won't believe, but the downside they'll only last about 10,000 miles at the most, but you get what you pay for.

The TBA differential brace is good enough you do not need to spend a lot of money on those braces, in relation to the power to weight ratio you will be putting down. You are accelerating a plus or minus 4,200lb car, and the Mustang GT 5.0 is 600lbs lighter, and the Camaro is 800lbs lighter, and the Corvette is 1,000lbs lighter, depending on years, so we are launching Heavy Metal!

Oh the drag strip requires a driveshaft safety loop if you go there, but the way our exhaust runs under the driveshaft even if it did come loose in the front I do not see how it could drop down to the road. Ry
 

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Good point about the exhaust catching the shaft. I still put a loop on
 

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Forgot: Once you go to a Limited Slip Differential you launch with Traction Control turned Off, with the Open 3.07 traction control is applying braking to the spinning rear tire attempting to stop it from spinning. Now if you are trying to go as fast off the line as you possibly can you don't want brakes being applied in the rear at all, but it will apply them even in Sport Mode showing traction off. Most brake pad wear happens on the front, but with traction control active trying to get off the line, my rear brake pads were worn to metal way before the front ever did, and that was from traction control being applied running 0 ~ 60s.
 

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Good point about the exhaust catching the shaft. I still put a loop on
I did too.

On my last exhaust change I was under the car looking at the layout of the exhaust under the driveshaft, and looking at the safety loop, and realized how could it possibly fall out of there.
 

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Discussion Starter · #11 ·

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Discussion Starter · #12 ·
As far as the wheel spin, what kind of tires you got on the back?
Michelins, with a I believe 500 rubber rating.

I was warned about the rubber ratings. But I put on what the internet said was the best. Should have listened to the members.
 

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Discussion Starter · #13 ·
Forgot: Once you go to a Limited Slip Differential you launch with Traction Control turned Off, with the Open 3.07 traction control is applying braking to the spinning rear tire attempting to stop it from spinning. Now if you are trying to go as fast off the line as you possibly can you don't want brakes being applied in the rear at all, but it will apply them even in Sport Mode showing traction off. Most brake pad wear happens on the front, but with traction control active trying to get off the line, my rear brake pads were worn to metal way before the front ever did, and that was from traction control being applied running 0 ~ 60s.
So the traction control still applies brake turned off. No wonder my 0-60s are not improving. Along with the fact that the more I drive the car the more torque it seems to develop. Although I can't figure out why it would. Maybe my butt dyno is off.
 

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So the traction control still applies brake turned off. No wonder my 0-60s are not improving. Along with the fact that the more I drive the car the more torque it seems to develop. Although I can't figure out why it would. Maybe my butt dyno is off.
No. With the traction control off, the programmed braking is turned off.
 

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Michelins, with a I believe 500 rubber rating.

I was warned about the rubber ratings. But I put on what the internet said was the best. Should have listened to the members.
I went the Toyo Proxes STIIIs which also have a 500 rubber composition but I went with those because I was initially driving to Texas from Georgia for work on a regular basis. Now that I'm back to flying because my new company pays for travel and when my wallet allows, I'll be throwing a set Nitto 555R2s on the rear. They have a 100 rubber composition and with their tread design, perform better in the wet than Mickey Thompson E/T Stret SSs if you're concerned about wet handling but both are great tires but like Ry said, you're only going to get about 10k miles out of either but when you put the juice to the goose...hang on partner cause you're going for a ride!
 

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Michelins, with a I believe 500 rubber rating.

I was warned about the rubber ratings. But I put on what the internet said was the best. Should have listened to the members.
Yep, you should have checked with the forum before you made the jump. Some of the most informed gear heads you'll ever get advise from lurk here
 

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So the traction control still applies brake turned off. No wonder my 0-60s are not improving. Along with the fact that the more I drive the car the more torque it seems to develop. Although I can't figure out why it would. Maybe my butt dyno is off.
No not if traction control is completely turned off, in the center display section of your speedometer area, it will say Electronic Stability Control is Disabled, you do that by holding down the traction control button until it beeps and shows that warning.

Sport Mode is kinda deceptive it shows at the center of the RPM guage a little symbol of a car with squigly lines with OFF under it, but traction control is not completely turned off in Sport Mode. Even in Sport mode you can hold down the traction control button until it beeps and you will get the Electronic Stability Control is disabled, then it is turned off!
 

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Just a friendly warning regarding turning traction control completely off, if your rear end is out of alignment at all, you could end up in a ditch, so be careful.
 

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Discussion Starter · #19 ·
I went the Toyo Proxes STIIIs which also have a 500 rubber composition but I went with those because I was initially driving to Texas from Georgia for work on a regular basis. Now that I'm back to flying because my new company pays for travel and when my wallet allows, I'll be throwing a set Nitto 555R2s on the rear. They have a 100 rubber composition and with their tread design, perform better in the wet than Mickey Thompson E/T Stret SSs if you're concerned about wet handling but both are great tires but like Ry said, you're only going to get about 10k miles out of either but when you put the juice to the goose...hang on partner cause you're going for a ride!
I did and was told not to do it but sometimes I don't hear good if you don't club me a little.
 
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Discussion Starter · #20 ·
No not if traction control is completely turned off, in the center display section of your speedometer area, it will say Electronic Stability Control is Disabled, you do that by holding down the traction control button until it beeps and shows that warning.

Sport Mode is kinda deceptive it shows at the center of the RPM guage a little symbol of a car with squigly lines with OFF under it, but traction control is not completely turned off in Sport Mode. Even in Sport mode you can hold down the traction control button until it beeps and you will get the Electronic Stability Control is disabled, then it is turned off!
Thanks, I did not know that. I thought if you hit the sport button it shut it all down.
 
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