2012 Camaro SS..Rear Diffrential..3.91 gears - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

beautyandbeast · 10-25-2012, 04:15 PM

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 ?

soloknight6 · 10-25-2012, 04:17 PM

Quote:

Originally Posted by beautyandbeast

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.

BaylorCamaro · 10-25-2012, 04:30 PM

Quote:

Originally Posted by soloknight6

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....

Medi0cr3 · 10-25-2012, 04:52 PM

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'

96MrBass · 10-25-2012, 04:55 PM

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.

beautyandbeast · 10-25-2012, 08:58 PM

Thanks guys for all your replies. I really appreciat it.

jbailey · 10-25-2012, 09:01 PM

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.

Snidely Whiplash · 12-30-2013, 12:21 AM

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.

JCunningham · 12-30-2013, 01:07 AM

who ever tuned your car can change the speedo calibration from 3.45 to 3.91. takes 5min and should be free.

Bo White · 12-30-2013, 07:33 AM

Quote:

Originally Posted by Snidely Whiplash

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.

Synner · 12-30-2013, 09:15 AM

Quote:

Originally Posted by Bo White

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.

AG1LE · 12-30-2013, 09:26 AM

Quote:

Originally Posted by Synner

And you're forgetting that the 1LE has different trans gearing so its not really a valid comparison.

Bo White · 12-30-2013, 09:57 AM

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?

Synner · 12-30-2013, 09:59 AM

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

10-25-2012, 04:15 PM	#1
beautyandbeast Drives: 2012 Camaro convertible SS RS Join Date: Oct 2012 Location: New Jersey Posts: 10 View My Garage	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 ?

10-25-2012, 04:52 PM	#4
Medi0cr3 Untamed Performance EPT Drives: 2011 2SS Join Date: Aug 2012 Location: El Paso Posts: 372	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' __________________ Night Fury Cam Borla LT Headers and Borla Cat Back ATAK 9in. diff with 4.11's, DSS Axles, and Alum Shaft Hurst Short-Shifter; Ideal Garage Master Cylinder H-E Street Slayer Twin Billet Clutch BMR: Adjustable; Trailing Arms, Toe Rods, Extreme Sway Bar. BMR Subframe Bushings. Strange Rear Coilovers and mounts Tuned by Rhino79

12-30-2013, 12:21 AM	#8
Snidely Whiplash Fight Crime, Drive Armed Drives: '14 2SS Yelo Maro, HD collection Join Date: Jun 2013 Location: NRH, TX Posts: 985	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. __________________ Bring back Sunoco 260 to the local station. Some folks STILL drive L-88s and need the good gas.

12-30-2013, 01:07 AM	#9
JCunningham Drives: 2017 2SS M6 Join Date: Jun 2013 Location: WNY Posts: 7,070	who ever tuned your car can change the speedo calibration from 3.45 to 3.91. takes 5min and should be free. __________________ real ZL1 wheels and brakes, 285/305 Michelin Pilot Super Sports, Pray ported Intake manifold, Soler Throttle Body, Rotofab intake, EFI Tuning Flex fuel kit, full American Racing Headers Exhaust, 1 7/8" w/ cats H pipe and mufflers. Full 1LE suspension, with BMR adjustable sway bars and links, GM aluminum cradle bushings, Hurst shifter with lighter reverse spring, TWM shifter knob, Tick level 1 transmission. I should have bought a ZL1

12-30-2013, 09:57 AM	#13
Bo White Drives: 2015 Summit White 2SS 1LE Join Date: Feb 2012 Location: Vance Alabama Posts: 8,019	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? __________________ Retired wanna be cylinder head porter 2015 2SS 1LE Clutch reservoir, Vararam DRX, ported TB, TSP 2" headers, MGW shifter Totalled: 2010 1SS Wilkes Performance/Eagle 416 shortblock, TSP custom valvetrain, PRC 260 heads, Edelbrock Pro Flo 102, th400 swap, 8" PTC 5500 stall= 535/435 at the wheels tuned Gen 3 Performance and Dyno 10.97 @ 124 full weight in 3100 DA CamaroFest X

10-25-2012, 04:55 PM	#5
96MrBass Drives: GM Join Date: Sep 2010 Location: Marydel, DE Posts: 1,321	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.

10-25-2012, 08:58 PM	#6
beautyandbeast Drives: 2012 Camaro convertible SS RS Join Date: Oct 2012 Location: New Jersey Posts: 10 View My Garage	Thanks guys for all your replies. I really appreciat it.

10-25-2012, 09:01 PM	#7
jbailey Drives: 2012 camaro Join Date: Aug 2011 Location: Loves Park, IL Posts: 23	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.

12-30-2013, 09:59 AM	#14
Synner Drives: cars Join Date: May 2011 Location: Oversneeze Posts: 4,544	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