Rear end gears
Thread Starter
Racer
Joined: Jun 2020
Posts: 427
Likes: 54
From: oroville ca
Rear end gears
My 2009 coupe C6 is Automatic and I have noticed that it kinda bogs a little around town and just a little when I am jumping on the freeway in the lower gears. I read that if I went with some lower gears in the rear end it would be a big difference and help eliminate that sort of low end bog that the automatics have. The transmission is fine but it does seem to want to shift a little early through the gears especially when I am just cruising around town and I am sure it is because GM wanted to get the gas mileage up for the c6 ls3. Well I have had enough of that and did not buy my corvette for good gas mileage, I was wondering if someone could share some of the knowledge or experiences with this issue or idea I have. I have the 2.56 rear end gears and I am thinking of going to the 2.73 which should take care of the slight bog in the lower gears and I really do not go 180 or 200 on the freeway ever so I dont need the tall gears. Has anyone done this who can shed some light on this for me or has anyone decided to go with the 2.73 as a option when ordering their vette? I believe the Z51 package came with 2.73 on the Auto..?? Thanks for taking the time to read ...
Supporting Vendor
Joined: Feb 2011
Posts: 3,520
Likes: 880
2024 C6 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (track prepared)
2019 C6 of Year Winner (track prepared)
My 2009 coupe C6 is Automatic and I have noticed that it kinda bogs a little around town and just a little when I am jumping on the freeway in the lower gears. I read that if I went with some lower gears in the rear end it would be a big difference and help eliminate that sort of low end bog that the automatics have. The transmission is fine but it does seem to want to shift a little early through the gears especially when I am just cruising around town and I am sure it is because GM wanted to get the gas mileage up for the c6 ls3. Well I have had enough of that and did not buy my corvette for good gas mileage, I was wondering if someone could share some of the knowledge or experiences with this issue or idea I have. I have the 2.56 rear end gears and I am thinking of going to the 2.73 which should take care of the slight bog in the lower gears and I really do not go 180 or 200 on the freeway ever so I dont need the tall gears. Has anyone done this who can shed some light on this for me or has anyone decided to go with the 2.73 as a option when ordering their vette? I believe the Z51 package came with 2.73 on the Auto..?? Thanks for taking the time to read ...
Race Director
Joined: Mar 2011
Posts: 13,262
Likes: 3,150
From: SW Florida
2021 C6 of the Year Finalist - Modified
Forget changing the rear differential gear ratio.
Get rid of the stock 1,700 rpm stall torque converter and replace it with a 2,800 - 3.000 rpm stall torque converter ... Circle-D converter is a good choice.
Big Big difference on how the car will launch !
Get rid of the stock 1,700 rpm stall torque converter and replace it with a 2,800 - 3.000 rpm stall torque converter ... Circle-D converter is a good choice.
Big Big difference on how the car will launch !
Instructor
Joined: Nov 2019
Posts: 226
Likes: 59
From: Farmington, MI
I have the 2.56 rear end gears and I am thinking of going to the 2.73 which should take care of the slight bog in the lower gears and I really do not go 180 or 200 on the freeway ever so I dont need the tall gears. Has anyone done this who can shed some light on this for me or has anyone decided to go with the 2.73 as a option when ordering their vette? I believe the Z51 package came with 2.73 on the Auto..?? Thanks for taking the time to read ...
However, RPM Transmissions offers 2.93 (14.4% shorter) and 3.15 (23% shorter) differential options for the A6 which would certainly make the car feel livelier, and not just stepping off from a standstill.
Thread Starter
Racer
Joined: Jun 2020
Posts: 427
Likes: 54
From: oroville ca
Well that sounds even better yes. I am guessing that all Z06 C6 come with 3.42 gears ? Where would be the best place to get the gears in your opinion ? As I do not know too much about rear end components or where to have them installed ? How much do they cost and should I get new ones or can I buy used gears ?
Melting Slicks
Joined: May 2018
Posts: 2,091
Likes: 600
From: Question Government
Race Director
Joined: Jul 2005
Posts: 12,028
Likes: 3,564
From: Central MO
I would probably step it up to a 3200 if I was going to make the change; I would absolutely go 3k minimum. There are plenty who would tell you to go 3600, and I've seen a few that run a 4k on the street.
Racer
Joined: Jun 2020
Posts: 274
Likes: 43
From: Vestavia Hills, AL
My 2009 coupe C6 is Automatic and I have noticed that it kinda bogs a little around town and just a little when I am jumping on the freeway in the lower gears. I read that if I went with some lower gears in the rear end it would be a big difference and help eliminate that sort of low end bog that the automatics have. The transmission is fine but it does seem to want to shift a little early through the gears especially when I am just cruising around town and I am sure it is because GM wanted to get the gas mileage up for the c6 ls3. Well I have had enough of that and did not buy my corvette for good gas mileage, I was wondering if someone could share some of the knowledge or experiences with this issue or idea I have. I have the 2.56 rear end gears and I am thinking of going to the 2.73 which should take care of the slight bog in the lower gears and I really do not go 180 or 200 on the freeway ever so I dont need the tall gears. Has anyone done this who can shed some light on this for me or has anyone decided to go with the 2.73 as a option when ordering their vette? I believe the Z51 package came with 2.73 on the Auto..?? Thanks for taking the time to read ...
I’d consider doing a different torque converter if I end up doing something of that nature with my C6. That’s just my experience though.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Race Director
Joined: Jul 2005
Posts: 12,028
Likes: 3,564
From: Central MO
One other thought; you might want to try a tune. The OEM torque reduction programmed in to "protect" the transmission results in built in hesitation. I removed most of the torque reduction and slightly tweaked both the engine and transmission parameters some. It made a big difference in responsiveness. And the Vitesse throttle controller also allowed me to tailor throttle tip in to my preference - SP4 - so it responds more like a cable driven throttle.
Thread Starter
Racer
Joined: Jun 2020
Posts: 427
Likes: 54
From: oroville ca
Yes I have heard that if you find a good tuner they can tune the transmission to shift later and to shift firmer if you want which is something I might want to wait until I install a trans cooler then go with the tune just to be safe.. ??...Thanks for all the input
Instructor
Joined: Nov 2019
Posts: 226
Likes: 59
From: Farmington, MI
Well that sounds even better yes. I am guessing that all Z06 C6 come with 3.42 gears ? Where would be the best place to get the gears in your opinion ? As I do not know too much about rear end components or where to have them installed ? How much do they cost and should I get new ones or can I buy used gears ?
Standard Auto: 2.56:1
Z51/ Grand Sport Auto: 2.73:1
All manuals (C6 Coupe, GS, Z06, ZR1): 3.42:1
As mentioned, aftermarket / other options include 2.93:1 and 3.15:1.
However the individual gear ratios for 1st etc. are different so the overall differences aren't that big.
To change the gear ratio you can either change just the ring and pinion gears themselves in your existing differential housing (a local transmission shop should be able to do this for you) or you buy a complete differential, either in exchange for yours or as an extra (keep your original).
A new set of ring and pinion gears might run you close to $1000, and maybe $500-1000 in labor to get them into your car (remove diff from car, replace and setup gears in diff, reinstall diff in car).
A performance upgraded rear diff unit from a specialist might cost you $2000-2500, and a few hundred to get it swapped out.
Last edited by Farmvette; Sep 26, 2021 at 10:09 PM.
Melting Slicks
Joined: Apr 2002
Posts: 2,397
Likes: 55
From: Dove Mountain, AZ
I had an 02 auto (4spd) and went from 3:15 to 3:73 and liked it alot, used the Diablo tuner to correct for gears. I would say go with 3:15's and it will be a fun ride and with a six spd auto there will be no problems on the highway.
All your gears will pull harder. If you go to low you will be spinning the tires all the time when you get into it. You will need to program it to correct for the gears. (Best cost effective way would be the 3:42's from a manual car, change the whole diff out)
All your gears will pull harder. If you go to low you will be spinning the tires all the time when you get into it. You will need to program it to correct for the gears. (Best cost effective way would be the 3:42's from a manual car, change the whole diff out)
Last edited by TXSTICK; Sep 27, 2021 at 10:16 AM.
Racer
Joined: Jun 2020
Posts: 274
Likes: 43
From: Vestavia Hills, AL
I had an 02 auto (4spd) and went from 3:15 to 3:73 and liked it alot, used the Diablo tuner to correct for gears. I would say go with 3:15's and it will be a fun ride and with a six spd auto there will be no problems on the highway.
All your gears will pull harder. If you go to low you will be spinning the tires all the time when you get into it. You will need to program it to correct for the gears. (Best cost effective way would be the 3:42's from a manual car, change the whole diff out)
All your gears will pull harder. If you go to low you will be spinning the tires all the time when you get into it. You will need to program it to correct for the gears. (Best cost effective way would be the 3:42's from a manual car, change the whole diff out)
Racer
Joined: Oct 2005
Posts: 441
Likes: 2
From: Austin TX
Just a heads up if you're interested.
I've got a 3.15 RPM built C6 diff for sale.
C6 diff out of a 2007 C6 with 30,000 miles.
RPM installed left and right hardened shafts.
RPM re-splined a 3.15 gear to mate with a 30-spline transmission.
Estimated the new gear has maybe 2000-3000 street miles.
LINK TO FOR SALE POST
I've got a 3.15 RPM built C6 diff for sale.
C6 diff out of a 2007 C6 with 30,000 miles.
RPM installed left and right hardened shafts.
RPM re-splined a 3.15 gear to mate with a 30-spline transmission.
Estimated the new gear has maybe 2000-3000 street miles.
LINK TO FOR SALE POST
Drifting
Joined: Apr 2001
Posts: 1,595
Likes: 358
A 6.6% change in gear ratio will be hardly noticeable and isn't worth the effort or expense, IMO. The cure for your problem is a good TQ converter as has been mentioned in this thread. Do your research and don't get caught up in higher higher higher stall RPMs unless you are seriously into racing (been there, done that.) A really good 2800-3500 stall would be my recommendation as a starting point for a street machine. 
Burning Brakes
Joined: May 2006
Posts: 1,110
Likes: 16
From: stuart fl
If it’s just a cruise around car get 3.42 gears and a tune. If you like/want to drag race it get the stall and/or gears.
From the way I read your post, it seems you just want a cruiser and couldn’t care less about drag racing it. If I’m right then get the 3.42 gears. Your car will run about 2000 rpm at 70 mph and I think mpgs will only go down a couple.
the 3.42s didn’t make my car much quicker at the drag strip but I loved the way it drove around town with them.
I just recently got rpm to build me another rearend for my car and it was $2500 with me sending my differential to them.
Good luck
From the way I read your post, it seems you just want a cruiser and couldn’t care less about drag racing it. If I’m right then get the 3.42 gears. Your car will run about 2000 rpm at 70 mph and I think mpgs will only go down a couple.
the 3.42s didn’t make my car much quicker at the drag strip but I loved the way it drove around town with them.
I just recently got rpm to build me another rearend for my car and it was $2500 with me sending my differential to them.
Good luck