3.91 rear end ratio question - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

BAH2SS · 02-07-2019, 05:58 PM

So i am planning to swap out my 3.45:1 to 3.91:1 same as the one which comes in 1LE. However, have a question abiut the different "Brands" out there. Cheapest I found was a company called RMS did anyone try them? And what do you guys think of the kit they sell. Motive ans Richmond also sell the 3.91 and they offer you three packages. My tunner suggested to go with Chevrolet performance kit but what do you guys think?

It's my daily and i doo highway pulls from time to time. Street race on weekends everything now and then. No track racing at all.

gsxrturbo · 02-07-2019, 06:42 PM

I just bought one out of a 1le on ebay for 1100 that only had 5000 miles on it,they aren't that bad to swap out,then I sold my old diff,going to run those 3.91's till I blow them out the back,I'll see how long it will last,im pushin 845 to the wheels,lol

Chris49066SS · 02-07-2019, 07:08 PM

https://www.camaro5.com/forums/showthread.php?t=542787

This is a really good thread with lots of good info from acammer. Z ended up going 4.10s, and I kinda wish I had too, after talking with them both. Give it a look. My vote is go 4.10 from Motive!

Mr_Draco · 02-07-2019, 08:19 PM

If I'm not mistaken, Motive is the company that makes the GM gears so they are one and the same.

For a stick shift, personally I would do 4.10's from Motive and leave the 3.91's for the autos.

rdavis · 02-07-2019, 09:37 PM

I have gm 3.91's, perfect for our manual cars.

What people don't realize is that the 1le car's transmissions are geared differently than a regular ss. The 3.91 was necessary to bring the overall ratios to equal the ss with 3.45's.

example:

1le 2.66 1st gear multiplied by 3.91 = 10.40 overall ratio.
SS 3.01 1st gear multiplied by 3.45 = 10.39 overall ratio
1le sixth gear .50 multiplied by 3.91 = 1.96 overall ratio
SS sixth gear .57 multiplied by 3.45 = 1.97 overall ratio

See the pattern.

Now the ss with 3.91's get better 3.01* 3.91 =11.77

A long time ago I read an article I believe by the late John Lingenfelter. He stated that his belief was the ideal overall first gear ratio for a street car is 12.0 to one. SS with 3.91s almost perfect. SS with 4.10s 12.34 very close also.

However the taller ratios in the 1le trans lend it to being stronger than the SS transmission.

gsxrturbo · 02-08-2019, 05:11 PM

didn't they have problems with the 4.10 gears rippin up the pinion?

CamaroFred · 02-08-2019, 09:35 PM

Quote:

Originally Posted by gsxrturbo

didn't they have problems with the 4.10 gears rippin up the pinion?

Richmond discontinued the 4.30s for that issue.
Any gears can be damaged with enough power and traction.

The 4.10 are a 19% increase over the 3.45
4.10/3.45 = 1.1884
3.91 = 13% increase.

L99s with 3.27 the 3.91 is a 20% increase. 3.73 ~14%.

qkslvr · 02-08-2019, 09:43 PM

I've had 3.91s in my SS for a few years and love it. Kind of a pain in the neighborhoods but overall I love it. Granted I had my rear done along with a bunch of other bolt ons so I could feel the the difference in them alone. Spend the extra to beef up the rear as well if your gonna be putting a bunch of power to it..

Taylortoons · 02-09-2019, 10:09 AM

Killer to have an SS in Bahrain. I was in Dubai last Fall and saw a bunch of V6 cars, but not many SS V8s. I agree with the 4.10. I went with the GM performance 3.91, but now wish I went with the lower 4.10s for highway driving in 6th gear.

Glassman66 · 02-10-2019, 09:01 AM

I had a 1994 Vette that I went to 4.10 from 3.45 gears, it was easily the best mod I ever did to that car. First through 4th the car was a beast, 5th and 6th became very usable.

steakmaker · 02-10-2019, 09:16 AM

I went with the GM performance 391's with the installation kit in my M6.The kit will include everything needed and a registered UPC sticker that goes on driver's side under the hood by the hinge.This states you have orginal Gm performance optional gears installed.Had mine in for 2yrs & love 'em.I lost about 2 mpg on a long cruise,still get 26mpg,but it kills you not to go wot.

zlathim · 02-10-2019, 09:29 AM

In my opinion, if you plan to do this job in your driveway on a budget and if you can find a complete diff with 3.91 gears from a 1LE, then that's probably the way to go. You would feel a nice increase in power.

If you are actually buying gears to install in your diff, then in my opinion it is foolish not to install 4.10 over 3.91 on a 6M SS. The cost is gonna be pretty much the same.
Putting 4.10s in my car was the best mod that I've done, hands down. It felt a more significant increase in power with my gears than I did when I installed my camshaft, or any other mod I've done.

These heavy cars are an absolute dog off the line. After you get used to 4.10s, you'll want a lower gear. Take as much as you can now.

Chris49066SS · 02-10-2019, 10:59 AM

Quote:

Originally Posted by Taylortoons

Killer to have an SS in Bahrain. I was in Dubai last Fall and saw a bunch of V6 cars, but not many SS V8s. I agree with the 4.10. I went with the GM performance 3.91, but now wish I went with the lower 4.10s for highway driving in 6th gear.

I have 3.91 but after talking to Z and Andrew, wish I had went with the 4.10s. And I have an auto. The cars are just so heavy

2010reddevil · 02-10-2019, 02:57 PM

Quote:

Originally Posted by Chris49066SS

I have 3.91 but after talking to Z and Andrew, wish I had went with the 4.10s. And I have an auto. The cars are just so heavy

Even with the 4.08 1st gear ratio of the auto? 3.91 still isn't enough?

02-07-2019, 05:58 PM	#1
BAH2SS Stigs Bahraini Cousin Drives: 2015 Camaro 2SS 1LE Join Date: Oct 2018 Location: Bahrain Posts: 222 View My Garage	3.91 rear end ratio question So i am planning to swap out my 3.45:1 to 3.91:1 same as the one which comes in 1LE. However, have a question abiut the different "Brands" out there. Cheapest I found was a company called RMS did anyone try them? And what do you guys think of the kit they sell. Motive ans Richmond also sell the 3.91 and they offer you three packages. My tunner suggested to go with Chevrolet performance kit but what do you guys think? It's my daily and i doo highway pulls from time to time. Street race on weekends everything now and then. No track racing at all. __________________ 2015 CAMARO 1LE

02-07-2019, 07:08 PM	#3
Chris49066SS Drives: 2010 SS L99 Join Date: Sep 2018 Location: Missouri Posts: 1,634	https://www.camaro5.com/forums/showthread.php?t=542787 This is a really good thread with lots of good info from acammer. Z ended up going 4.10s, and I kinda wish I had too, after talking with them both. Give it a look. My vote is go 4.10 from Motive! __________________ Previous PB:11.079 @ 122.99mph.. New setup time: TBD The 11.079 pass: https://youtu.be/pz27Zq54t_E Build thread - www.camaro5.com/forums/showthread.php?t=555371

02-07-2019, 09:37 PM	#5
rdavis Drives: 2012 SS Join Date: Feb 2016 Location: Lubbock Texas Posts: 121	I have gm 3.91's, perfect for our manual cars. What people don't realize is that the 1le car's transmissions are geared differently than a regular ss. The 3.91 was necessary to bring the overall ratios to equal the ss with 3.45's. example: 1le 2.66 1st gear multiplied by 3.91 = 10.40 overall ratio. SS 3.01 1st gear multiplied by 3.45 = 10.39 overall ratio 1le sixth gear .50 multiplied by 3.91 = 1.96 overall ratio SS sixth gear .57 multiplied by 3.45 = 1.97 overall ratio See the pattern. Now the ss with 3.91's get better 3.01* 3.91 =11.77 A long time ago I read an article I believe by the late John Lingenfelter. He stated that his belief was the ideal overall first gear ratio for a street car is 12.0 to one. SS with 3.91s almost perfect. SS with 4.10s 12.34 very close also. However the taller ratios in the 1le trans lend it to being stronger than the SS transmission. __________________ 2012 2SS/RS 6speed, Howards asa cam on 113lsa Stainless works LT's, NPP exhaust, Z28 Cai, 3.91 gears. Tuned by Blue Thunder 2 racing Lubbock Texas.

02-08-2019, 09:43 PM	#8
qkslvr Drives: 2010 ABM 1SS M6 NON RS Join Date: May 2010 Location: Rapid City, SD Posts: 669 View My Garage	I've had 3.91s in my SS for a few years and love it. Kind of a pain in the neighborhoods but overall I love it. Granted I had my rear done along with a bunch of other bolt ons so I could feel the the difference in them alone. Spend the extra to beef up the rear as well if your gonna be putting a bunch of power to it.. __________________ 2010 Aqua Blue 1SS KWC 3pc forged, Seibon hood, ZL front end, MGW, ARH full exhaust w/ Doug Thorley axle back, BTR4, Roto-fab, LSXR 102, NW 102, 3.91s 2018 GMC Sierra (Stone Blue metallic) 2016 Streetglide (Crushed Ice Pearl) 2018 Indian Scout (Bronze Smoke)

02-09-2019, 10:09 AM	#9
Taylortoons Drives: 2011 2SS/RS LS3 Join Date: Apr 2017 Location: Dallas Posts: 482	Killer to have an SS in Bahrain. I was in Dubai last Fall and saw a bunch of V6 cars, but not many SS V8s. I agree with the 4.10. I went with the GM performance 3.91, but now wish I went with the lower 4.10s for highway driving in 6th gear. __________________ GPI Built Procharger D-1/13 PSI/Race Intercooler/SS3 Cam Kit/Kooks LTH/X- pipe/FIC 1050/E85/3.91 gears/Centerforce Dual Disc clutch/Flowmaster Outlaw/775whp/680tqSOLD

02-07-2019, 06:42 PM	#2
gsxrturbo Drives: 2010 ss Join Date: Oct 2015 Location: windom mn Posts: 337	I just bought one out of a 1le on ebay for 1100 that only had 5000 miles on it,they aren't that bad to swap out,then I sold my old diff,going to run those 3.91's till I blow them out the back,I'll see how long it will last,im pushin 845 to the wheels,lol

02-07-2019, 08:19 PM	#4
Mr_Draco Drives: 2SS/RS Join Date: Sep 2008 Location: Western North Carolina Posts: 7,182	If I'm not mistaken, Motive is the company that makes the GM gears so they are one and the same. For a stick shift, personally I would do 4.10's from Motive and leave the 3.91's for the autos.

02-08-2019, 05:11 PM	#6
gsxrturbo Drives: 2010 ss Join Date: Oct 2015 Location: windom mn Posts: 337	didn't they have problems with the 4.10 gears rippin up the pinion?

02-10-2019, 09:01 AM	#10
Glassman66 Drives: 2014 Camaro 2SS/RS 1le Join Date: Jan 2017 Location: Denver Co Posts: 260	I had a 1994 Vette that I went to 4.10 from 3.45 gears, it was easily the best mod I ever did to that car. First through 4th the car was a beast, 5th and 6th became very usable. __________________ 2014 Camaro 1LE SS/RS THE MISTRESS

02-10-2019, 09:16 AM	#11
steakmaker Drives: '10 Camaro SS,Jeep Commander Hemi Join Date: Mar 2010 Location: Cicero,NY Posts: 567	I went with the GM performance 391's with the installation kit in my M6.The kit will include everything needed and a registered UPC sticker that goes on driver's side under the hood by the hinge.This states you have orginal Gm performance optional gears installed.Had mine in for 2yrs & love 'em.I lost about 2 mpg on a long cruise,still get 26mpg,but it kills you not to go wot.

02-10-2019, 09:29 AM	#12
zlathim Drives: 2010 Camaro 2SS/RS M6 Join Date: May 2009 Location: Idaho Posts: 726	In my opinion, if you plan to do this job in your driveway on a budget and if you can find a complete diff with 3.91 gears from a 1LE, then that's probably the way to go. You would feel a nice increase in power. If you are actually buying gears to install in your diff, then in my opinion it is foolish not to install 4.10 over 3.91 on a 6M SS. The cost is gonna be pretty much the same. Putting 4.10s in my car was the best mod that I've done, hands down. It felt a more significant increase in power with my gears than I did when I installed my camshaft, or any other mod I've done. These heavy cars are an absolute dog off the line. After you get used to 4.10s, you'll want a lower gear. Take as much as you can now. __________________ GPI SS2; EE E2 catch can; SP 1 7/8" LT Headers w/ hfc; FM AT 3" cat-back; CAI Cold Air Intake; AEM Wideband Tuned by GPI McCleod RXT; MGW flat stick; Ram Clutch slave cylinder & hydraulic adjuster BMR cradle & diff bushings, trailing arms, toe rods & upper control arm bushings Hotchkis sub-frame brace Stop Tech Z-23 brakes 4.10 gears, Eaton Truetrac, LPW diff cover Best 1/4 mile 12.073 @ 115.68 mph 3,300 ft DA