PCM re-program required for MN6 switch to 3.73s?
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From: Frisco, TX
PCM re-program required for MN6 switch to 3.73s?
I've seen this topic discussed above, and the consensus seemed to be that for the MN6 that is switched to 3.73s, no PCM reprogram is required. Well, my new 3.73s just got delivered :cool: :cool:, and I'd like to know if there's a clear answer. I'd be particularly interested in hearing from those with MN6 cars that have switched to the 3.73. Did you do a re-program, and if not, does your PCM give any odd code as a result of the swap?
Thanks.
Thanks.
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Re: PCM re-program required for MN6 switch to 3.73s? (flipm)
From everything I've heard and read, it has always pointed to the fact that the MN6 does not require reprograming.
The A4 does, though.
The A4 does, though.
Racer
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Re: PCM re-program required for MN6 switch to 3.73s? (Mike Mercury)
The speed sensor is on the carrier at rotates a the same RPM per MPH regardless of the gear ratio. Thus you do not need programming for the speedometer since it is not effected.
You do need programming to change the shift points for an A4.
You do need programming to change the shift points for an A4.
Melting Slicks
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Re: PCM re-program required for MN6 switch to 3.73s? (gsxguy)
The speed sensor is on the carrier at rotates a the same RPM per MPH regardless of the gear ratio. Thus you do not need programming for the speedometer since it is not effected.
You do need programming to change the shift points for an A4.
You do need programming to change the shift points for an A4.
-Jeremy
[Modified by Godspeed, 11:17 AM 1/9/2002]
Melting Slicks
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From: Bethlehem PA
St. Jude Donor '03-'05-'06-'08-'10
Re: PCM re-program required for MN6 switch to 3.73s? (Godspeed)
Steve/guys, I am an MN6'er that went with 3.73s and did nothing with the programming and/or speedometer AND no codes... the car just runs great! While I do have the Powerloader II programming, it was installed prior to the rear change. The bottom three gears are awesome with the 3.73s...wouldn't hesitate recommending the change.
Joe
[Modified by C54FUN, 11:14 AM 1/9/2002]
Joe
[Modified by C54FUN, 11:14 AM 1/9/2002]
Thread Starter
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From: Frisco, TX
Re: PCM re-program required for MN6 switch to 3.73s? (C54FUN)
Thanks to all for your responses. :cheers:
Joe -- since the swap, have you ever tried to confirm that your speedometer is accurate? Thanks again. :)
Joe -- since the swap, have you ever tried to confirm that your speedometer is accurate? Thanks again. :)
Melting Slicks
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From: Bethlehem PA
St. Jude Donor '03-'05-'06-'08-'10
Re: PCM re-program required for MN6 switch to 3.73s? (SteveL2)
Steve, yes I have and it's right on. I would say the R's are up about 150 on average, at speed, when compared to the 3.42s. Good luck with your mod. When the gears are in you'll have to let me know what you think. Hope your rear rubber is good, cause I now spin the Pilot Sports at will and if I stomp on the gas, in first, I induce wheel hop. Pressing on the gas smoothly just brings the power forth uninterrupted. You jaws are going to ache from all the smiles...I know mine did! BTW still haven't been to track since the change, but will let you know of the results when I do.
Joe
[Modified by C54FUN, 11:37 AM 1/9/2002]
Joe
[Modified by C54FUN, 11:37 AM 1/9/2002]
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Re: PCM re-program required for MN6 switch to 3.73s? (C54FUN)
[QUOTE]Steve/guys, I am an MN6'er that went with 3.73s and did nothing with the programming and/or speedometer AND no codes... the car just runs great! While I do have the Powerloader II programming, it was installed prior to the rear change. The bottom three gears are awesome with the 3.73s...wouldn't hesitate recommending the change."
True your car runs good, BUT------ your true speed is INACCURATE since you did not reprogram.
True your car runs good, BUT------ your true speed is INACCURATE since you did not reprogram.
Melting Slicks
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Re: PCM re-program required for MN6 switch to 3.73s? (Ed Ut)
Steve/guys, I am an MN6'er that went with 3.73s and did nothing with the programming and/or speedometer AND no codes... the car just runs great! While I do have the Powerloader II programming, it was installed prior to the rear change. The bottom three gears are awesome with the 3.73s...wouldn't hesitate recommending the change."
True your car runs good, BUT------ your true speed is INACCURATE since you did not reprogram.
True your car runs good, BUT------ your true speed is INACCURATE since you did not reprogram.
JC
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Re: PCM re-program required for MN6 switch to 3.73s? (The One)
True your car runs good, BUT------ your true speed is INACCURATE since you did not reprogram.
But, A4's do.
Unless my memory is failing......
I will try to confirm this. We neet C5 Tech to chime in on this one.
Melting Slicks
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Re: PCM re-program required for MN6 switch to 3.73s? (Mike Mercury)
I still believe (although I am not always 100% correct) that if you change the gears the car will run just fine, not throw any codes, but the speedo will be slightly off. The reprogram will correct this inaccuracy. It's similiar to if you changed the size of your tires, you would need to correct the PCM or the speedo would be slightly off. If you can live with the inaccuracy the difference between 3.42 and 3.73 isn't that great.
Melting Slicks
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From: Bethlehem PA
St. Jude Donor '03-'05-'06-'08-'10
Re: PCM re-program required for MN6 switch to 3.73s? (C54FUN)
Guys, I recognize my assessment of speedometer error was not totally scientific, but acceptable. What I did was run my car alongside my wife's for speed correlation and used the measured mile on our parkway for further collaboration. Bottomline IMHO, either the difference is so small or it is right on. For me, I am comfortable with the observed result. The folks at CARTEK that did the install claimed the "no effect on speedometer aaccuracy" as a result of how the C5 senses it...honestly, I don't remember all these facts. Best I can do....
Joe
Joe
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Re: PCM re-program required for MN6 switch to 3.73s?
The MN6 does NOT require a reprogram.
On the 3.42 gear, you have 12 teeth on the pinion and 41 on the ring.
On the 3.73 gear, you have 11 teeth on the pinion and 41 on the ring.
The speed sensor reads the rotation of the ring gear. Thus, since the ring is the same for both, no programming is required on the manual trans..
HOWEVER, for the automatics, the relationship between engine rpm and mph does change, and thus has an impact on the shift points. You DO need to program for this...
I've put 3.73's in my last two MN6 coupes.. never had to change program, speedo is dead on, I've had it laser confirmed..
On the 3.42 gear, you have 12 teeth on the pinion and 41 on the ring.
On the 3.73 gear, you have 11 teeth on the pinion and 41 on the ring.
The speed sensor reads the rotation of the ring gear. Thus, since the ring is the same for both, no programming is required on the manual trans..
HOWEVER, for the automatics, the relationship between engine rpm and mph does change, and thus has an impact on the shift points. You DO need to program for this...
I've put 3.73's in my last two MN6 coupes.. never had to change program, speedo is dead on, I've had it laser confirmed..
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Re: PCM re-program required for MN6 switch to 3.73s? (SteveL2)
I installed the 3.73's in my car with no Computer tuning. I checked it against a GPS unit and another totally stock C5 HUD. Turns out that the speedo is off by exactly "1 MPH" at speeds from 30 mph to 105 mph.
I can live with that. :yesnod: I Hope you can too. ;)
vetterdstr :cheers:
I can live with that. :yesnod: I Hope you can too. ;)
vetterdstr :cheers:
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Re: PCM re-program required for MN6 switch to 3.73s? (SteveL2)
Nevrenuf hit the nail on the head...The speed sensor takes generated pulses from the ring gear tooth reluctor...Because the ring gears are the same size there is no change in the speedo...It is the pinion gear that rotates at a different speed on the two different ratios,which accounts for the change in RPM...
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From: Frisco, TX
Re: PCM re-program required for MN6 switch to 3.73s? (C-5 TECH)
Just wanted to say thanks to all who gave their thoughts on this post, and of course for relieving my concern because now I know I can proceed with the install. Now it's just too bad I'm not closer to C5-Tech so I could be sure to have it installed by someone who knows their stuff. :D
Cheers. :cheers:
Cheers. :cheers:
Melting Slicks
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Re: PCM re-program required for MN6 switch to 3.73s? (SteveL2)
Steve.. just run over to MTI and have them drop it in.. It doesnt take very long.. 3 hours or so.. really a very simple installation!
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Re: PCM re-program required for MN6 switch to 3.73s? (nevrenuf)
Before we put this thread to bed, it is worth stating that different diameter tires will change the speedometer reading because it's "downstream" of the sensor.
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Re: PCM re-program required for MN6 switch to 3.73s? (jschindler)
jschindler: YOU SIR, are correct. I used the the poorman's gear change, went to a 285/35-18 rear tire, changing the effective gear from a 3.42 to a 3.53, and with a wider tire to boot. Better acceleration, but the speedo is off by 3%. :cheers: