2.73 to 3.15 gear replacement (HELP)
Thread Starter
Melting Slicks
Joined: Jan 2004
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From: NW Chicago, IL/Clearwater Beach, FL
2.73 to 3.15 gear replacement (HELP)
i'm going to upgrade my gear from a 2.73 to a 3.15 swap out the hole unit, now do i have to do any computer reprograming or shift point reprograms? some are saying NO! ( THE COMPUTER WILL AUTOMATICLY TAKE THE UPGRADE) the 3.15 is a option gear from GM just put in and car will be fine, and some are saying the if i put in the 3.15 i have to buy a programer or have a V.I.N. from a corvette that came with a 3.15 installed from the factory, so that V I N can be programed into my computer at the dealer........i have a 2000 automatic coupe
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Re: 2.73 to 3.15 gear replacement (rollinred)
i'm going to upgrade my gear from a 2.73 to a 3.15 swap out the hole unit, now do i have to do any computer reprograming or shift point reprograms?
The 2.73 to 3.15 upgrade is one that the Chevrolet dealer can handle with their GM programing tool; called the Tech Tool 2.
But this doesn't mean they will still do it. My local dealer quoted me $60 for such a reprog.
BUT, the GM reprog tool can not program in a rear axle ratio that wasn't available from the factory (with the type of transmission you have). And the A4 only came with either the 2.73 or 3.15. The GM programer will not accept entries for any other ratios other than 2.73 or 3.15
The factory PCM has different values in it for the 2.73 and the 3.15 ratios; so the data needed is not already in your PCM now.
Or if you go with a more radical ratio ... say the 3.42 or 3.73 you'll need to go elsewhere (than your Chevy dealer) for a reprog or buy an aftermarket programmer yourself. No matter what ratio you vary from. if you are starting with the 2.73 then you will have to reprog
.
[Modified by Mike Mercury, 6:39 PM 3/22/2004]
Thread Starter
Melting Slicks
Joined: Jan 2004
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From: NW Chicago, IL/Clearwater Beach, FL
Re: 2.73 to 3.15 gear replacement (Mike Mercury)
mike you're saying that if i do the 3.15 the dealer can reprogram my computer with a tech tool 2 ? BUT, the GM reprog tool can not program in a rear axle ratio that wasn't available from the factory like a 3.42 or 3.73 (with the type of transmission you have). if i understand this right with the trans i have, and go with only a 3.15 there wont be a problem, it can be done with a tech tool 2.......
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St. Jude Donor '04
Re: 2.73 to 3.15 gear replacement (birch64)
received the 3.15 for $100.00 from a 2000 with only 9000mi couldn't pass up the deal.
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Re: 2.73 to 3.15 gear replacement (runamuk)
if i understand this right with the trans i have, and go with only a 3.15 there wont be a problem, it can be done with a tech tool 2.......
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Melting Slicks
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From: NW Chicago, IL/Clearwater Beach, FL
Re: 2.73 to 3.15 gear replacement (Mike Mercury)
thanks for you're help mike, time to start looking around tomorrow in the chicago nw suburbs,for a dealer the will reprogram the computer, after i change the gear.
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Re: 2.73 to 3.15 gear replacement (Mike Mercury)
if i understand this right with the trans i have, and go with only a 3.15 there wont be a problem, it can be done with a tech tool 2.......
yes, but many Chevy dealers won't mess with this sort of stuff - even though they are capable of doing it.
yes, but many Chevy dealers won't mess with this sort of stuff - even though they are capable of doing it.
While I am sure that this is not the case everywhere, just be advised that some dealers may balk.
Perhaps you can answer this for me Mike. Why is programming necessary when going from 2.73s to 3.15 or higher. I understand that one will hit the rev limiter before the car shifts from 1st to 2nd if no programming is done.......but why???? I know I must be missing something here, but it seems to me that the tranny would shift at a given RPM or predetermined speed no matter the rear end. A friend of mine who owns a C4 asked me this and I could not give him an answer.
[Modified by EB20003, 7:48 PM 3/22/2004]
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Re: 2.73 to 3.15 gear replacement (EB20003)
WOT PCM shifting of the A4 is mainly based on MPH. So, assume that your 2.73 currently shifts WOT from first to second at 50 mph and this is at 5800rpm. When you swap to the 3.15, the MPH at 5800 rpm is now 42mph. The PCM will continue engine acceleration until programmed 50mph is reached. But at 47mph your engine now is at redline and the rev limiter will close the throttle to limit the rpm. You'll never reach the 50mph where the PCM is programmed to command a shift. The rev limiter stops the car from reaching the programmed MPH shift point.
When you reprog a C5 (because of a rear axle ratio change), you enter in new -lower MPH shift points to account for the MPH difference.
and then there's the P1870 PCM "slip error" code to avoid - but that's not related to WOT shifting.
.
[Modified by Mike Mercury, 9:44 PM 3/22/2004]
When you reprog a C5 (because of a rear axle ratio change), you enter in new -lower MPH shift points to account for the MPH difference.
and then there's the P1870 PCM "slip error" code to avoid - but that's not related to WOT shifting.
.
[Modified by Mike Mercury, 9:44 PM 3/22/2004]
Thread Starter
Melting Slicks
Joined: Jan 2004
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From: NW Chicago, IL/Clearwater Beach, FL
Re: 2.73 to 3.15 gear replacement (birch64)
stopped by the dealer today, and they told me if i have a V I N from a 2000 coupe with same options and trans, they can only program from a 2.73 to a 3.15. or down nothing else.......... he told me the charge would be between 30 to 60 minutes labor charge no more than $68.00 for one hour if it took that long for the reprogram.......... gona put the gear in and drive 4 blocks to the chevy dealer and get it reprogramed...................... thanks for the advise mike
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From: Wilmington NC
Re: 2.73 to 3.15 gear replacement (birch64)
When I upgraded from a 2.73 to a 3.15, I went to the local dealership and they charged me $35 for a new GM factory 3.15 tune. It's very easy for them to do so make sure you do not overpay. All they have to do is hook their tech tool up to your car, download the information in your computer, and send it to GM. GM will make you a new tune and send it to the dealership. Hope this helps.
Also, my pcm eventually adjusted itself to the new gears. It took a couple hundred miles to do so. I only got the GM reflash for more piece of mind. I could tell a difference though after the new tune. My car is also a 2000 A4.
Adam
[Modified by PewterVette, 3:33 AM 3/24/2004]
[Modified by PewterVette, 3:34 AM 3/24/2004]
Also, my pcm eventually adjusted itself to the new gears. It took a couple hundred miles to do so. I only got the GM reflash for more piece of mind. I could tell a difference though after the new tune. My car is also a 2000 A4.
Adam
[Modified by PewterVette, 3:33 AM 3/24/2004]
[Modified by PewterVette, 3:34 AM 3/24/2004]
Thread Starter
Melting Slicks
Joined: Jan 2004
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From: NW Chicago, IL/Clearwater Beach, FL
Re: 2.73 to 3.15 gear replacement (PewterVette)
so the dealer can take my V I N and have GM upgrade it for a 3.15 gear i dont need a V I N form another 2000 coupe that came from the factory with a 3.15 already in it?
[Modified by birch64, 3:40 AM 3/24/2004]
[Modified by birch64, 3:40 AM 3/24/2004]
Racer
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From: Wilmington NC
Re: 2.73 to 3.15 gear replacement (Mike Mercury)
What I mean by that is that after the 3.15s were installed, my car would hit the rev limiter at wide open throttle since the shifts points were off. I would do this once, then drive the car for about 50 miles, and then see if it still hit the rev limiter at wot. Also, every time I dropped below about 40 mph, my car would trigger the slippage code and I would have to pull over, reset the code, and then continue driving. After about 200 miles of driving my car eventually shifted great and never hit the rev limiter. Also, no codes. I drove my car for a long time after it finally shifted perfectly and I wasn't going to bother getting a new tune but decided to just to be on the same side.
Hope I am making sense.
[Modified by PewterVette, 4:40 AM 3/24/2004]
Hope I am making sense.
[Modified by PewterVette, 4:40 AM 3/24/2004]
Racer
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From: New Orleans La
Re: 2.73 to 3.15 gear replacement (birch64)
I honestly don't think you should change to 3.15's.... With 2.73's you can dead hook on the street and no one will ever beat you from a roll unless they just happen to catch you between 50-60. I raced a guy today from a 30 mph roll with a 12 second flat T/A w/ a vigilante 3600 3.73 gears and full bolt ons. I smoked him 5 times in a row:) He wouldn't believe that my vette was stock. The more and more racing I do with these gears the more I love them. It must be the weather or something cause with AH off I can spin the tires @35 mph+ in my auto heh(my old T/A certainly couldn't even come close to that stock).
Racer
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From: Wilmington NC
Re: 2.73 to 3.15 gear replacement (birch64)
Yes, that is correct. All I did was make an appointment to have it done and take my car to the dealership. You do not need a VIN # from a 3.15 car.
The only downside when I had this done is that it took a week for the dealership to receive my new 3.15 tune from GM. This was because the guy who usually does this work was out of town. I bet you will not have this problem though.
I'll look in the glove box for my records tomorrow to confirm this but I think the 3.15 tune I got from GM is called a VCI #. Basically, you will get the same tune back from GM that is currently in your car with the only change being your shift points and whatever else is required when going to a 3.15.
[Modified by PewterVette, 4:55 AM 3/24/2004]
The only downside when I had this done is that it took a week for the dealership to receive my new 3.15 tune from GM. This was because the guy who usually does this work was out of town. I bet you will not have this problem though.
I'll look in the glove box for my records tomorrow to confirm this but I think the 3.15 tune I got from GM is called a VCI #. Basically, you will get the same tune back from GM that is currently in your car with the only change being your shift points and whatever else is required when going to a 3.15.
[Modified by PewterVette, 4:55 AM 3/24/2004]
Safety Car
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From: Murphy TX
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Re: 2.73 to 3.15 gear replacement (EB20003)
Perhaps you can answer this for me Mike. Why is programming necessary when going from 2.73s to 3.15 or higher. I understand that one will hit the rev limiter before the car shifts from 1st to 2nd if no programming is done.......but why???? I know I must be missing something here, but it seems to me that the tranny would shift at a given RPM or predetermined speed no matter the rear end. A friend of mine who owns a C4 asked me this and I could not give him an answer.
No one should be under the impression that the PCM "adapts" or "learns" new values for shift points and so forth. There are some adaptive cells related to pressure and duration, but they work as adjustments relative to a defined target.
You guys having trouble coaxing the dealer into being helpful are taking donuts, right? :jester
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Re: 2.73 to 3.15 gear replacement (ToplessTexan)
Hope I am making sense.
I can't explain your outcome. :confused:
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Re: 2.73 to 3.15 gear replacement (Mike Mercury)
Thanks for the explanations Mike and Texan, for I have always wondered this. I knew that programming was necessary and that " reprogramming was necessary for calibrating the speedometer" was the wrong answer, but untill now didn't know the right answer.
So it seems that as long as its not WOT that a shift into second gear is possible assuming the target MPH is reached before the car redlines?
Thanks again.
[Modified by EB20003, 11:11 AM 3/24/2004]
So it seems that as long as its not WOT that a shift into second gear is possible assuming the target MPH is reached before the car redlines?
Thanks again.
[Modified by EB20003, 11:11 AM 3/24/2004]