Need clarification on gear swap! - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

CyberGreyConvertible · 02-13-2016, 12:00 PM

Hey, guys. I'm looking to swap out my 3.27's for either 3.73's or 3.91's, but I really can't find a definitive answer of which ratio to choose.

My car:

• 2012 SS, Auto
• Only bolt ons (LT headers) + tune
• NOT planning on getting it cammed

So, which do you think I should go with? I've done searching around the forums, but I still can't decide.. Some people say that 3.91's are best for cammed engines, for example.

All in all; I can't decide which gear ratio to choose! I appreciate all input here,

Thanks!

blakjak55 · 02-13-2016, 12:07 PM

Rule of thumb seems to be 3:91's for N/A and 3:73's for FI.

Mine's an M6 but even if I went FI I'd keep my 3:91's and put the money in suspension for grip.

rontammy0 · 02-13-2016, 03:03 PM

Quote:

Originally Posted by CyberGreyConvertible

Hey, guys. I'm looking to swap out my 3.27's for either 3.73's or 3.91's, but I really can't find a definitive answer of which ratio to choose.

My car:

• 2012 SS, Auto
• Only bolt ons (LT headers) + tune
• NOT planning on getting it cammed

So, which do you think I should go with? I've done searching around the forums, but I still can't decide.. Some people say that 3.91's are best for cammed engines, for example.

All in all; I can't decide which gear ratio to choose! I appreciate all input here,

Thanks!

Im getting 391s in the spring....my tuner recommends them. They have done alot of those with great results. So i would say 391s.

Apex Motorsports · 02-13-2016, 05:51 PM

Quote:

Originally Posted by CyberGreyConvertible

Hey, guys. I'm looking to swap out my 3.27's for either 3.73's or 3.91's, but I really can't find a definitive answer of which ratio to choose.

My car:

• 2012 SS, Auto
• Only bolt ons (LT headers) + tune
• NOT planning on getting it cammed

So, which do you think I should go with? I've done searching around the forums, but I still can't decide.. Some people say that 3.91's are best for cammed engines, for example.

All in all; I can't decide which gear ratio to choose! I appreciate all input here,

Thanks!

There isn't necessarily a right or wrong answer. If you don't plan on doing more than bolt on mods then 3.91s will give you the most bang for your buck. 1st gear is really short though.

By upgrading the factory 3.27s in the stock A6 equipped Camaro SS to the 3.73s you will realize an equivalent torque gain of approximately 15% or 62 lb.-ft. of torque and cruise at 2050 RPM at 70 MPH. By upgrading to the 3.91s you will realize an equivalent torque gain of approximately 20% or 82 lb.-ft. of torque and cruise at 2150 RPM at 70 MPH.

JCunningham · 02-13-2016, 05:58 PM

he has a auto 3.73 is recommended. 3.91 for stick.

mfarhan_amin · 02-13-2016, 06:52 PM

I have 3.91 with Kooks LT, CAI and Tune. I am running VTC on SP6. Just Amazing Torque and Throttle Response.
But Traction is a big problem specially launching from 0 in 1st Gear. 2nd Gear do Good.
Launching from 20MPH is Awesome. Seat of the Pants feeling is Simply WOW.

Trob85 · 02-13-2016, 07:20 PM

3:91 for a boosted 4l80 car.

christianchevell · 02-13-2016, 08:36 PM

The deal is the production of the 1le made the 3:91s cheaper ..... so do what you want the gears are not much more drastic from a 3:73 .

olblue75 · 02-13-2016, 08:40 PM

The 3.73 are to automatics what the 3.91s are to the manual cars.
Like stated above it makes 1st gear really short and don't think there is a speedo recal for automatics for either gear set from GM.

OHIOSS · 02-13-2016, 10:19 PM

I have an M6 in my SS and I changed to a 3.91 rear end. It made a huge difference in the performance, one of the best mods I've ever done.

olblue75 · 02-13-2016, 10:35 PM

Quote:

Originally Posted by OHIOSS

I have an M6 in my SS and I changed to a 3.91 rear end. It made a huge difference in the performance, one of the best mods I've ever done.

RIGHT!!!!!
Get a Z/28 intake and see how you like them then it's huge!!!

jergarr · 02-14-2016, 06:48 PM

Quote:

Originally Posted by CyberGreyConvertible

Hey, guys. I'm looking to swap out my 3.27's for either 3.73's or 3.91's, but I really can't find a definitive answer of which ratio to choose.

My car:

• 2012 SS, Auto
• Only bolt ons (LT headers) + tune
• NOT planning on getting it cammed

So, which do you think I should go with? I've done searching around the forums, but I still can't decide.. Some people say that 3.91's are best for cammed engines, for example.

All in all; I can't decide which gear ratio to choose! I appreciate all input here,

Thanks!

I have the 3.91's in my L99 and I wish I had done them sooner. My only real complaint is the higher rpm's on the highway can get annyoung at times but that's the trade off. I ran a 12.4 1/4 mile with 1.85 60' this past fall. At the moment I do plan on going with an aftermarket cam in the next year but the gears by themselves are a good mod.

jergarr · 02-14-2016, 07:04 PM

Quote:

Originally Posted by olblue75

The 3.73 are to automatics what the 3.91s are to the manual cars.
Like stated above it makes 1st gear really short and don't think there is a speedo recal for automatics for either gear set from GM.

I was worried about the short first gear but it's definitely not undriveable by any means. My installer was able to recalibrate the speedo as well.

rontammy0 · 02-14-2016, 07:47 PM

Quote:

Originally Posted by jergarr

I have the 3.91's in my L99 and I wish I had done them sooner. My only real complaint is the higher rpm's on the highway can get annyoung at times but that's the trade off. I ran a 12.4 1/4 mile with 1.85 60' this past fall. At the moment I do plan on going with an aftermarket cam in the next year but the gears by themselves are a good mod.

Did you track it before your 12.4 et. I'm wondering how the 391s will help my et and 60ft. Thanks

02-13-2016, 12:00 PM	#1
CyberGreyConvertible Dunder Mifflin Inc. Drives: 2012 2SS/RS Convertible Join Date: Jan 2014 Location: Cincinnati Posts: 468	Need clarification on gear swap! Hey, guys. I'm looking to swap out my 3.27's for either 3.73's or 3.91's, but I really can't find a definitive answer of which ratio to choose. My car: • 2012 SS, Auto • Only bolt ons (LT headers) + tune • NOT planning on getting it cammed So, which do you think I should go with? I've done searching around the forums, but I still can't decide.. Some people say that 3.91's are best for cammed engines, for example. All in all; I can't decide which gear ratio to choose! I appreciate all input here, Thanks!

02-13-2016, 12:07 PM	#2
blakjak55 drinks virgil's Drives: 2010 2SS M6 Join Date: Feb 2014 Location: Missouri Posts: 448	Rule of thumb seems to be 3:91's for N/A and 3:73's for FI. Mine's an M6 but even if I went FI I'd keep my 3:91's and put the money in suspension for grip. __________________ 2010 2SS/RS M6 - CAI Intake - Borla Stinger - VTC - 3.91's Eibach Sways - LG ZR28's - BMR Springs - 285/35 Squared

02-13-2016, 05:58 PM	#5
JCunningham Drives: 2017 2SS M6 Join Date: Jun 2013 Location: WNY Posts: 7,069	he has a auto 3.73 is recommended. 3.91 for stick. __________________ 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

02-13-2016, 06:52 PM	#6
mfarhan_amin Drives: Camaro 2SS 2013 Join Date: Sep 2014 Location: Jeddah Saudi Arabia Posts: 149	I have 3.91 with Kooks LT, CAI and Tune. I am running VTC on SP6. Just Amazing Torque and Throttle Response. But Traction is a big problem specially launching from 0 in 1st Gear. 2nd Gear do Good. Launching from 20MPH is Awesome. Seat of the Pants feeling is Simply WOW. __________________ Camaro 2013 2SS/RS L99 VICTORY RED VMAX PORTED THROTTLE BODY, ROTO-FAB CAI, FLOWMASTER OUTLAW AXLE-BACK WITH J-PIPES. VITESSE THROTTLE CONTROLLER. 1LE 3.91 GEARS. KOOKS 1 7/8 LTs, CAT DELETE, GPI SS2 VVT CAM, ATI 10% UDP, MELLING HIGH VOLUME HIGH PERFORMANCE OIL PUMP

02-13-2016, 07:20 PM	#7
Trob85 Svt lol Drives: 2011 ss inferno orange blown Join Date: Jan 2012 Location: Topeka Posts: 2,312	3:91 for a boosted 4l80 car. __________________ plasti dip is not a mod.......and a cold air intake doesn't make you fast!

02-13-2016, 08:36 PM	#8
christianchevell old school chevy rodder Drives: 2021 zl1 a-10 WildCherry Join Date: Jul 2012 Location: Oregon Posts: 5,622 View My Garage	The deal is the production of the 1le made the 3:91s cheaper ..... so do what you want the gears are not much more drastic from a 3:73 . __________________ 2021 Wild Cherry ZL1 A10, Sunroof, Data,Red Carbon Interior, Nav, RotoFab Big Gulp , Elite x2ultra, Borla ATAK, Driveshaft shop, BMR susp, Speed covers, intercoolers, ATI , 2650 MAG, DSX lid, 103 NW, TSP Longtubes & cats, LPE, 1le mods, ,LME cover, Katech pump and chain, Trunnions, BTR stage 2, LPE boostapump, Gforce, Speed eng , Granetteli, etc etc

02-13-2016, 08:40 PM	#9
olblue75 Drives: 2010 2SS/RS Join Date: Dec 2009 Location: Clarksville Tennesse. Posts: 6,148	The 3.73 are to automatics what the 3.91s are to the manual cars. Like stated above it makes 1st gear really short and don't think there is a speedo recal for automatics for either gear set from GM. __________________ Orange Krush II 1LE Front sway bar, Splitter, shocks and struts, Z28 dual mode mufflers, Intake, UCA Bushings, and Toresen 3.91 Diff. 1 piece DSS Drive Shaft, ZL1/C7 Calipers, and 32mm JPSS Rear Bar. ASC race spec splitter and wicker. 6th Gen M017 Wheels. Stainless Works 1 7/8 LTs. DSE and PAFDT Suspension components.

02-13-2016, 10:19 PM	#10
OHIOSS Russ Drives: Yukon Denali, Charger, CamaroSS Join Date: Jun 2009 Location: Ohio Posts: 2,811	I have an M6 in my SS and I changed to a 3.91 rear end. It made a huge difference in the performance, one of the best mods I've ever done.