2.59 to 3.07 rear diff
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 46
Likes: 0
From: Eau Claire WI
2.59 to 3.07 rear diff
If I am changing from the 2.59 on my 87 auto to a 3.07 anything else I need besides speedo gears? Also anyone know a place to get a 3.07 at a reasonable price? Either new or used.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
If you want the mileage indicator to work correctly and not sure what else but there is always something you may need to tell the ECU about the gear change other wise it does not know the correct speed or distance traveled for mileage reading too.
Dave
Dave
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 46
Likes: 0
From: Eau Claire WI
I thought on the 94-96 u had to reflash them to correct gear changes on on the l98 just change the speedo gear? I hav a burned chip in the car now I suppose I could get it re burned if needed.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Speed input is determined by what comes from the VSS ; correct speedo gears ( for diff ratio ) give correct input signal
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
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
Le Mans Master
Joined: Oct 2008
Posts: 9,758
Likes: 49
From: Houston Texas
If you are changing the gear in the diff you need one. If you are talking about the whole diff then you are OK. I found a good low mileage diff from a forum member for a very good price. In my experience this forum is one of the best places to buy.
CL=Craigslist.org
CL=Craigslist.org
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
As the gear ratio changes the thickness of the crownwheel changes.
To accommodate that fact , the factory uses different thickness carriers that only take a certain range of gears;
2 series (< 3.00 , 3 series (3.07 - 3.73 ) , etc.
When you move from one series to another like you wish to do ,
then you either need ( for OEM " thin " gear sets) the appropriate carrier, in your case a 3 series carrier
or the aftermarket makes " thick" gears that make up the space on the crown wheel itself ( as in the crownwheel is thicker )
so you can fit 3 series gears onto a 2 series carrier
To accommodate that fact , the factory uses different thickness carriers that only take a certain range of gears;
2 series (< 3.00 , 3 series (3.07 - 3.73 ) , etc.
When you move from one series to another like you wish to do ,
then you either need ( for OEM " thin " gear sets) the appropriate carrier, in your case a 3 series carrier
or the aftermarket makes " thick" gears that make up the space on the crown wheel itself ( as in the crownwheel is thicker )
so you can fit 3 series gears onto a 2 series carrier
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 46
Likes: 0
From: Eau Claire WI
Are you saying reguardless I need different thicknesses or if i go with the whole diff case and all I am covered? I was hoping to get a complete unit and bolt up not change out just the gears
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Le Mans Master
Joined: Jul 2009
Posts: 6,381
Likes: 66
From: SF bay area C.A.
C4 of the Year Finalist
Advanced
Joined: Jul 2010
Posts: 78
Likes: 1
From: Cape Town
The jump from 2.59 to 3.07 is rather mild , you really need 3.5 or so to really wake the car up... basically going from 2.59 to 3.54 or so is the same as "losing" overdrive but with 4 gears and not 3 in D.
Team Owner
Joined: Sep 2003
Posts: 25,394
Likes: 2,741
Is this a "complete with bat-wing" or just the differentiala?
If it's just the differential the shipping will be quite reasonable - if it's a complete w/bat-wing I'd consider shipping in two packages. I've generally used FEDEX Ground and to keep it reasonable carry it to a FEDEX Office location (not an agent or affiliate) and if you can ship it to a comercial address (business). Using affiliates or agents and residential delivery increase the fees significantly.
Pack well in heavy cardboard or maybe use a plastic tote.
$80 will easily cover the ship and it could be something closer to $60. It certainly shouldn't be a "deal-breaker"!
Last edited by WVZR-1; Jun 11, 2012 at 05:12 AM.
Racer
Joined: Oct 2010
Posts: 414
Likes: 0
From: Phoenix Arizona
When you are ready to make the change, I'd also consider going to 3.73 gears. I have the Dana 36 with the 3.73 gears hooked up to the 700r4. I now have a LS3 Hot Cam crate engine in the car but the diff and gears were there when I still had the LT1 in my '92. I love the gears. Gas mileage suffers but the extra performance makes it worth it. I get about 17.5 mpg overall and that was also true with the LT1. At 85mph I'm running about 2900 rpm but it really gets out of the whole quickly. Just my 2 cents.
Thread Starter
Intermediate
Joined: Jun 2011
Posts: 46
Likes: 0
From: Eau Claire WI
So I have found a Dana 36 3.07 rear from a fellow member batwing and all. Now i was doing some more research today and am confussed.... Do I just need to change the speedo gear in my case going from 35 teeth to 42 teeth I believe or do I need a new speed sensor as well? I've heard it both ways but from what I can see the speed sensor drive gear for all 87's has 17 teeth. I was from the beginning under the impression if I swapped out the whole case for a new one I just needed to do the speedo driven gear.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
Not with a rev restricted TPI engine
http://forums.corvetteforum.com/1568185079-post21.html
http://forums.corvetteforum.com/1568186621-post24.html
Awesome SOTP difference with the 3.07's vs 2.59
http://forums.corvetteforum.com/1568185079-post21.html
http://forums.corvetteforum.com/1568186621-post24.html
Awesome SOTP difference with the 3.07's vs 2.59