Differential Gear Ratio Advice

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Nov 16, 2018 | 08:40 AM

brownrd

Thread Starter

Instructor

Joined: May 2017

Posts: 114

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From: Ontario

Differential Gear Ratio Advice

Need your advice on best choice for differential gear ratio. Cammed 2000 M6, so stock ratio is 3.42. Common choices are 3.73, 3.90 and 4.10. Car will be used mostly as a fun street machine with very occasional HPDE track duty. Will have some highway time but no long distance trips planned. Right now I find that 6th is pretty much useless unless I am willing to either lug the engine or risk a ticket for speeding.

Nov 16, 2018 | 10:28 AM

Pumba

Melting Slicks

Joined: Sep 2003

Posts: 2,458

Likes: 105

From: Northville Michigan

First, I am making some assumptions about your Corvette. I assume that you have the standard Tremec transmission with the 2.66:1 first gear and the 0.50:1 sixth gear.

For a final drive ration gear set I would recommend a 4.10:1. I would also suggest that you consider changing your sixth gear to a 0.42:1. Why? Because by changing the sixth gear to 0.42:1 your overall gearing in sixth gear is the same as a 3.42 ring and pinion with a 0.50:1 sixth gear. If you need a recommendation for a place to purchase the ring and pinion in Canada, I cannot help with that. The only place you can purchase a 0.42:1 sixth gear is at Liberty Performance. Call (586) 469-1149 and talk to Craig Liberty. Mention Jim Riley or Howard Kell and he will remember when he made the gear.

Good luck.

Nov 16, 2018 | 11:25 AM

Pounder

1/4 mile/AutoX

Joined: Jun 2014

Posts: 11,442

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From: Buffalo Texas

4.10's !!!! I agree 6th is worthless !!!!

Nov 16, 2018 | 11:44 AM

vettenuts

Team Owner

Joined: Mar 1999

Posts: 22,025

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From: At the beach in little Rhody

I have been happy with my 3.90's but the 4.10's wouldn't be a bad choice either. Sixth is much more usable.

Nov 16, 2018 | 11:44 AM

brownrd

Thread Starter

Instructor

Joined: May 2017

Posts: 114

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From: Ontario

Thanks guys. Being an M6 this transmission does have the 2.66 1st gear. The M12 used in the Z06 is clearly more performance oriented. Found the attached chart showing the differences. So it looks like my best choice is between 3.90 and 4.10. Would be great to find a built diff from a part out!

------------M12.......3.42.....M6.....3.42.....3.73. ....3.90
First-------2.97.....10.16....2.66.....9.1.....9.92. ...10.37
Second---2.07......7.08....1.78.....6.09....6.64. ....6.94
Third------1.43......4.89.....1.30....4.45....4.85. ....5.07
Fourth----1.00......3.42.....1.0......3.42....3.73 .....3.90
Fifth------0.84......2.87.....0.74.....2.53....2.76 .....2.89
Sixth-----0.56......1.92.....0.50.....1.71....1.87 .....1.95

Nov 16, 2018 | 12:16 PM

493lszosix

Pro

Joined: Dec 2015

Posts: 661

Likes: 182

From: Knoxville TN

I’ve ran 4.10 with an m6 trans and it didn’t feel low enough, definitely go 4.10’s, I’m running 4.10 in m12 trans now and love it!

Nov 16, 2018 | 12:21 PM

sstonebreaker

Le Mans Master

Joined: Mar 2006

Posts: 5,775

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From: Texas

You mentioned cammed, I suggest having the heads modified to bump compression. I had a 234/246 cam and when I had the compression bumped to 11.6, my torque increased by over 100 ft/lbs at 2500 rpm. Made driving around town much more enjoyable. And I had 3.90 gears in that car, btw.

Nov 16, 2018 | 12:46 PM

brownrd

Thread Starter

Instructor

Joined: May 2017

Posts: 114

Likes: 19

From: Ontario

Quote:

Originally Posted by sstonebreaker

Good input. I am running around 10.8 or 10.9 compression now (243's + 0.05" shave to clean up + Cometic 0.040" head gasket). This seems to work well on 91 octane pump gas and with the cam I am running (Ed Curtis Street Sweeper HT specs ground by Cam Motion) it provided nice PTV clearance.