2.73 > 3.42 diff change - tuning needed?
Thread Starter
Burning Brakes
Joined: Mar 2020
Posts: 776
Likes: 246
From: KY
2.73 > 3.42 diff change - tuning needed?
Hello all,
I would post this in the tuning thread but it gets so little traffic I'm going to post it here in the Tech section. If mods decide to move it, so be it. I posted the same on DiabloSport (*as I have a Trinity 2 tuner) and have included Mike's answer below my question.
I'm getting ready to do a 2.73 > 3.42 differential swap on my 2002 Corvette A4 base. It is currently running the 91 octane tune (always run 93 octane as that is what they have in my area) with no other adjustments. Car is stock other than cat back exhaust. Can I make the programming changes needed for the 2.73 > 3.42 differential swap or are the parameters locked so only a custom tuner can do it? If I can do it what are the parameters that need changes and what are the changes?
From Mike at DiabloSport - you can make them, and honestly most C5s as i recall do not even need any change in the tune as they measure speed after the diff.
But going through many threads here I find info like those below and I need to know if I need to do anything tuning-wise and can I do it with the Trinity 2 that I have?With a gear swap no speedo change is required However you will need a "shift point correction" for both WOT and P/T shifts
If your car had a 2.73 rear gear then you would need a MINUS 25% for both P/T up/down shifts as well as for WOT up/down shifts
If your car had a 3.18 gear then you MINUS 8%
and
For 3.42 Gears set the following parameters:
1-2 Upshift MPH 41
2-3 Upshift MPH 80
3-4 Upshift MPH 130
2-1 downshift 36
3-2 downshift 79
4-3 downshift 118
Rev limits @ 6480
Rev Limits ON @ 6479
I would post this in the tuning thread but it gets so little traffic I'm going to post it here in the Tech section. If mods decide to move it, so be it. I posted the same on DiabloSport (*as I have a Trinity 2 tuner) and have included Mike's answer below my question.
I'm getting ready to do a 2.73 > 3.42 differential swap on my 2002 Corvette A4 base. It is currently running the 91 octane tune (always run 93 octane as that is what they have in my area) with no other adjustments. Car is stock other than cat back exhaust. Can I make the programming changes needed for the 2.73 > 3.42 differential swap or are the parameters locked so only a custom tuner can do it? If I can do it what are the parameters that need changes and what are the changes?
From Mike at DiabloSport - you can make them, and honestly most C5s as i recall do not even need any change in the tune as they measure speed after the diff.
But going through many threads here I find info like those below and I need to know if I need to do anything tuning-wise and can I do it with the Trinity 2 that I have?With a gear swap no speedo change is required However you will need a "shift point correction" for both WOT and P/T shifts
If your car had a 2.73 rear gear then you would need a MINUS 25% for both P/T up/down shifts as well as for WOT up/down shifts
If your car had a 3.18 gear then you MINUS 8%
and
For 3.42 Gears set the following parameters:
1-2 Upshift MPH 41
2-3 Upshift MPH 80
3-4 Upshift MPH 130
2-1 downshift 36
3-2 downshift 79
4-3 downshift 118
Rev limits @ 6480
Rev Limits ON @ 6479
Safety Car
Joined: Aug 2011
Posts: 4,447
Likes: 409
From: Portland OR
They shift by mph at part throttle. Not RPM.
so lower gears, the rpm will be high before it shifts.
Full throttle looks for mph, then waits for rpm.
Follow Diablosport advice. No changes needed. See what happens. Then report back.
so lower gears, the rpm will be high before it shifts.
Full throttle looks for mph, then waits for rpm.
Follow Diablosport advice. No changes needed. See what happens. Then report back.
Safety Car
Joined: Mar 2005
Posts: 3,755
Likes: 1,214
From: Wisconsin
get it tuned, you will damage your trans if you keep driving it, TCC slip table and the WOT shift MPH value need adjustment, your shift points will be off
the rpm vs mph will be way off and set a trans slipping code
the rpm vs mph will be way off and set a trans slipping code
Last edited by feeder82; Oct 9, 2020 at 08:25 PM.
Drifting
Joined: Sep 2009
Posts: 1,862
Likes: 594
From: Prescott, Arizona
Yes. When I went from 3.15 to 3.73 rear drive on my A4, it would hit the rev limiter in second and still not shift. I had A&A Corvette re program the PCM, which fixed the problem.
https://www.aacorvette.com/
https://www.aacorvette.com/
Race Director
Joined: May 2006
Posts: 10,846
Likes: 462
From: EAST TENNESSEE
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
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