3.42 install for auto trans without reprogram...
Thread Starter
Safety Car
Joined: Mar 2001
Posts: 4,233
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From: Laguna Niguel Ca
3.42 install for auto trans without reprogram...
I hate to keep beating this dead horse... but... My differential arrives tomorrow and I'm planning on having it installed in the next few days. I'm told by some that you don't really need to reprogram shift points or anything and some say you do. My budget is very limited right now and I am thinking about just installing them and see how it works. Any input is appreciated. 
Thread Starter
Safety Car
Joined: Mar 2001
Posts: 4,233
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From: Laguna Niguel Ca
Drifting
Joined: Dec 2011
Posts: 1,422
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From: San Gabriel Valley California
St. Jude Donor '14-'15
I hate to keep beating this dead horse... but... My differential arrives tomorrow and I'm planning on having it installed in the next few days. I'm told by some that you don't really need to reprogram shift points or anything and some say you do. My budget is very limited right now and I am thinking about just installing them and see how it works. Any input is appreciated.
But I've never heard knowledgeable guys here on the forum write/say you 'don't' need a retune of the shift points, after a gear/differential change. Maybe I missed that, though. It happens.
It's above my pay grade, but all I've seen written on the forum, guys who know much more about this than me, say it is necessary. Looking forward to feed back here for your question.
I wonder who told you that is wasn't necessary? Based on what ?
Don
Instructor
Joined: Mar 2006
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From: ames ia
At part throttle it would likely be okay. You might end up with weird shifts, and torque converter lockup being weird, but likely okay.
If your going from a 3.15 to a 3.42 you might get away with it at WOT, its a small enough change
2.73 to 3.42.... I'll bet you end up banging a rev limiter and getting hung up shifts..
For wot shifting the car looks for an RPM and MPH threshold... It will not command a shift until both parameters are met.
If you change to a 3.42 gear from something like a 2.73, your RPM will be met much sooner compared to what it used to be, and the car will still be waiting for a MPH threshold to hit...
from a 3.15, the change is small enough, and the fudge room large enough, you might be okay, but it wouldn't surprise me if again once in awhile you still hit a rev limiter while it waits to shift.
If your going from a 3.15 to a 3.42 you might get away with it at WOT, its a small enough change
2.73 to 3.42.... I'll bet you end up banging a rev limiter and getting hung up shifts..
For wot shifting the car looks for an RPM and MPH threshold... It will not command a shift until both parameters are met.
If you change to a 3.42 gear from something like a 2.73, your RPM will be met much sooner compared to what it used to be, and the car will still be waiting for a MPH threshold to hit...
from a 3.15, the change is small enough, and the fudge room large enough, you might be okay, but it wouldn't surprise me if again once in awhile you still hit a rev limiter while it waits to shift.
Thread Starter
Safety Car
Joined: Mar 2001
Posts: 4,233
Likes: 0
From: Laguna Niguel Ca
At part throttle it would likely be okay. You might end up with weird shifts, and torque converter lockup being weird, but likely okay.
If your going from a 3.15 to a 3.42 you might get away with it at WOT, its a small enough change
2.73 to 3.42.... I'll bet you end up banging a rev limiter and getting hung up shifts..
For wot shifting the car looks for an RPM and MPH threshold... It will not command a shift until both parameters are met.
If you change to a 3.42 gear from something like a 2.73, your RPM will be met much sooner compared to what it used to be, and the car will still be waiting for a MPH threshold to hit...
from a 3.15, the change is small enough, and the fudge room large enough, you might be okay, but it wouldn't surprise me if again once in awhile you still hit a rev limiter while it waits to shift.
If your going from a 3.15 to a 3.42 you might get away with it at WOT, its a small enough change
2.73 to 3.42.... I'll bet you end up banging a rev limiter and getting hung up shifts..
For wot shifting the car looks for an RPM and MPH threshold... It will not command a shift until both parameters are met.
If you change to a 3.42 gear from something like a 2.73, your RPM will be met much sooner compared to what it used to be, and the car will still be waiting for a MPH threshold to hit...
from a 3.15, the change is small enough, and the fudge room large enough, you might be okay, but it wouldn't surprise me if again once in awhile you still hit a rev limiter while it waits to shift.
Team Owner
Joined: Sep 2001
Posts: 23,283
Likes: 906
From: Lake Elsinore, CA
What GoatKart said - you will be bangin' the rev limiter if you don't reprogram. 
I did this mod a few years ago (2.73-->>3.42) and did the reprogram with EFILive before it ever left the garage. I increased the shift pressures ~15% as well. Car drove awesome. These gears were combined with a Yank SS3200 stall which made it even better.
http://forums.corvetteforum.com/c5-g...mega-pics.html
I did this mod a few years ago (2.73-->>3.42) and did the reprogram with EFILive before it ever left the garage. I increased the shift pressures ~15% as well. Car drove awesome. These gears were combined with a Yank SS3200 stall which made it even better.
http://forums.corvetteforum.com/c5-g...mega-pics.html
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Sounds like a great mod for your car. Best of luck getting the gears installed and the car programmed to take advantage of the change.
Burning Brakes
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At part throttle it would likely be okay. You might end up with weird shifts, and torque converter lockup being weird, but likely okay. If your going from a 3.15 to a 3.42 you might get away with it at WOT, its a small enough change 2.73 to 3.42.... I'll bet you end up banging a rev limiter and getting hung up shifts.. For wot shifting the car looks for an RPM and MPH threshold... It will not command a shift until both parameters are met. If you change to a 3.42 gear from something like a 2.73, your RPM will be met much sooner compared to what it used to be, and the car will still be waiting for a MPH threshold to hit... from a 3.15, the change is small enough, and the fudge room large enough, you might be okay, but it wouldn't surprise me if again once in awhile you still hit a rev limiter while it waits to shift.
Team Owner
Joined: Sep 2001
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From: Lake Elsinore, CA
Speedo is not affected and PCM does not have to be reprogrammed for different diff ratio. The sensor reads off the output so, whatever speed it's going is automatically registered properly on the speedo.
Melting Slicks
Joined: Nov 2003
Posts: 3,011
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From: Dublin GA
I guess I disagree about not needing the programming. You need RPM and mph to shift at WOT. That is a big gear change and WILL affect the rpm quite a bit. I would also think you would need to have them "rematch" the mph/rpm points, since it will change the relationship. (for example, now, 6000 may be 38 mph, but with new gears, 6000 may be 32 mph)
I would go ahead and do the tune, and have them raise the shift points a couple hundred RPM to take advantage of the higher revving of the 3.42.
I would go ahead and do the tune, and have them raise the shift points a couple hundred RPM to take advantage of the higher revving of the 3.42.
Racer
Joined: Jul 2013
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From: '97 Coupe & '07 Coupe in Allentown, PA
I went from 2.73 to 3.42 this summer with a Yank SS3600 converter. The re-program for the new gears is a very basic change. ECS did my swap and charged $150 for the tune. They also do mail order tunes for the same price. Cheaper than buying a handheld and doing it yourself.
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St. Jude Donor '12-'13-'14
I went from 2.73 to 3.42 this summer with a Yank SS3600 converter. The re-program for the new gears is a very basic change. ECS did my swap and charged $150 for the tune. They also do mail order tunes for the same price. Cheaper than buying a handheld and doing it yourself.
You still need a unit to install the tune.
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Not when you send the PCM in for our $149 mail in tune special. PCM's usually turned around the same day.
Oh and yes you must tune the car when switching gears in an auto. Well if you want it to drive correctly anyway.
link to the tuning thread;
https://www.corvetteforum.com/forums...nly-149-a.html
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Thread Starter
Safety Car
Joined: Mar 2001
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From: Laguna Niguel Ca
I talked to the service manager at Corvette Mike today. They are going to do the install. The programming is just an additional $150... So it's on!!!! Just waiting for an appt.
Melting Slicks
Joined: Feb 2014
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From: chicago area IL.
I swapped from 3.42 to 3.73 and didnt not program any thing was done at RPM trans, but i'm a manual not sure if that matters? speedometer is dead on checked with gps
before i committed to the swap I ask they guys and they said it reads on a wheel sensor I think it was and no programing is needed
before i committed to the swap I ask they guys and they said it reads on a wheel sensor I think it was and no programing is needed