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V8 and V6 Transmissions / Driveline (6L80 / 6L50 / TR6060 / AY6) Driveshafts | Differentials | Gears | Rearends | Clutch | Shifters

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Old 10-25-2012, 04:15 PM   #1
beautyandbeast
 
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2012 Camaro SS..Rear Diffrential..3.91 gears

Greetings everyone,
I own a 2012 Camaro SS manual transmission. Just got the heads and cams done. I am planning to change the rear diffrential witn 3.91 gears. Do i have to flash the computer after I get the 3.91 gears installed or for manual transmission it does not matter ?
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Old 10-25-2012, 04:17 PM   #2
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Quote:
Originally Posted by beautyandbeast View Post
Greetings everyone,
I own a 2012 Camaro SS manual transmission. Just got the heads and cams done. I am planning to change the rear diffrential witn 3.91 gears. Do i have to flash the computer after I get the 3.91 gears installed or for manual transmission it does not matter ?
Im sure you would need to tune the car afterwards. I believe changing the gear ratio will throw off your speedo.
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Old 10-25-2012, 04:30 PM   #3
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Im sure you would need to tune the car afterwards. I believe changing the gear ratio will throw off your speedo.
I'm sure it will, going to low profile tires messed with my speedo....
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Old 10-25-2012, 04:52 PM   #4
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A tuner such as Diablo Sport Intune its easy, just change the axle ratio and your set. You can even change tire size =]. I know SCT is popular and has better datalogging for engine idle than diablos'
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Old 10-25-2012, 04:55 PM   #5
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Mine is in the shop having 3.91's installed as we post and yes I am told it needs a tune at least for speedo.
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Old 10-25-2012, 08:58 PM   #6
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Thanks guys for all your replies. I really appreciat it.
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Old 10-25-2012, 09:01 PM   #7
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Yes, I just changed my gear and had to have the tune adjusted.
You will really like the 3.91's. it really balances the feel of the cam change.
I had a cam,cai,tune and headers done and did not like the 3.45 gear afterwards.
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Old 12-30-2013, 12:21 AM   #8
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That's a lot of gear for a 3.01 first gear transmission. You may want to go with a lower profile tire and/or 3.73 gears. If you gotta have the 3.91s, get some 30" tall rear tires.
With an 11.77 overall first gear on sticky (or drag radial) stock diameter tires, you're gonna break driveline parts. A hard launch will have you shifting before you're sure the car is going straight. Bad juju.
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Old 12-30-2013, 01:07 AM   #9
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who ever tuned your car can change the speedo calibration from 3.45 to 3.91. takes 5min and should be free.
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Old 12-30-2013, 07:33 AM   #10
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Quote:
Originally Posted by Snidely Whiplash View Post
That's a lot of gear for a 3.01 first gear transmission. You may want to go with a lower profile tire and/or 3.73 gears. If you gotta have the 3.91s, get some 30" tall rear tires.
With an 11.77 overall first gear on sticky (or drag radial) stock diameter tires, you're gonna break driveline parts. A hard launch will have you shifting before you're sure the car is going straight. Bad juju.
No, 3.91 is a great street gear for our cars. Even GM thinks so since its a factory gear for the 1LE. The Pontiac G8 GXP comes factory with 3.70 gears with a shorter tire than the Camaro.
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Old 12-30-2013, 09:15 AM   #11
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No, 3.91 is a great street gear for our cars. Even GM thinks so since its a factory gear for the 1LE. The Pontiac G8 GXP comes factory with 3.70 gears with a shorter tire than the Camaro.
And you're forgetting that the 1LE has different trans gearing so its not really a valid comparison.
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Old 12-30-2013, 09:26 AM   #12
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And you're forgetting that the 1LE has different trans gearing so its not really a valid comparison.
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Old 12-30-2013, 09:57 AM   #13
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Actually wasn't aware of that but I do know the GXP has the same tranny gearing as the SS. Thanx for the info on the 1LE tranny info, what is its gearing?
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Old 12-30-2013, 09:59 AM   #14
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1LE MM6 w/ 3.91
1st gear ratio: 2.66 10.42
2nd gear ratio: 1.78 6.97
3rd gear ratio: 1.30 5.09
4th gear ratio: 1.00 3.91
5th gear ratio: 0.74 2.90
6th gear ratio: 0.50 1.96

SS M10 w/ 3.45 w/ 3.91
1st gear ratio: 3.01 10.38 11.77
2nd gear ratio: 2.07 7.14 8.09
3rd gear ratio: 1.43 4.93 5.59
4th gear ratio: 1.00 3.45 3.91
5th gear ratio: 0.84 2.90 3.28
6th gear ratio: 0.57 1.97 2.23
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Old 12-30-2013, 10:01 AM   #15
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Thanx, that's what forums are for!
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Old 12-30-2013, 10:30 AM   #16
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While I love the heck out of my 3.91 gears for street driving I must admit that for me I have made a hard to launch car even a little harder to launch. Plus as mentioned I am on top of the rev limiter in first gear in a heart beat. Like most things in life its a compromise. I'm glad I put the gears in. They compliment my cam by giving more tq down low with the cam kicking in higher up. However, I'll need a lot of practice to ever get good at a hole shot launch.
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Old 12-30-2013, 10:54 AM   #17
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Some info in this thread might be useful

http://www.camaro5.com/forums/showthread.php?t=329619
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