gears
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From: upstate central new york
gears
if you were to re gear you truck (i have 3.73 possible change to 4.30) does the pcm need to be reflashed or what else would have to be done 2000 cc 4x4 lariat 265/75 16
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From: Gladwin,Mi
Originally Posted by 900rr
if you were to re gear you truck (i have 3.73 possible change to 4.30) does the pcm need to be reflashed or what else would have to be done 2000 cc 4x4 lariat 265/75 16
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From: Gladwin,Mi
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From: central Louisiana
for a gear change ONLY, you do not have to correct your speedo! on SD's the only time you have to get into speedo corections is when you change TIRE SIZE!
with a 265/75/16 tire (stock) you do not have to change/re-calibrate your speedo.
your carrier has a tooth gear or "tone gear" that the sensor reads a pattern off of. unlike the days of speed being read off of the trans tail shaft, the sensor on the rear diff reads rotation of the tone gear, instead of the rotations of the drive shaft!
if ALL you want is a speedo recalibration (for future refernce), save some $ and buy a Superlift TruSpeed. check the good ol "scam"bay and you can probably find one for less than $150 (i did)!
with a 265/75/16 tire (stock) you do not have to change/re-calibrate your speedo.
your carrier has a tooth gear or "tone gear" that the sensor reads a pattern off of. unlike the days of speed being read off of the trans tail shaft, the sensor on the rear diff reads rotation of the tone gear, instead of the rotations of the drive shaft!
if ALL you want is a speedo recalibration (for future refernce), save some $ and buy a Superlift TruSpeed. check the good ol "scam"bay and you can probably find one for less than $150 (i did)!
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Like Team Mudd said... with this bit of wisdom added... a gear change from 3.73:1 to 4.30:1 should be followed by a re-boot of the PCM by disconnecting the battery to clear the modified fuel and ignition curves and other adaptive learning tables back to the default mode. Then over the next series of driving cycles, all the adaptive learning will re adjust the maps to the new RPM vs. speeds, loads, and shift strategy.
As stated above, the speedo will still read accurately with a re-gear on the SuperDuty trucks because Axle rotations are what is being sensed... all you have changed is drive shaft RPM per Axle RPM....
If you make the tires taller or shorter (attached to the Axle) then you need to re calibrate the PCM... Ford can change it over a fairly wide range but is limited to the various legitimate tire sizes that the Factory would ever supply up to around 34~35 inch diameter in the 601 Rev per mile range...if you install 36 or taller with a 580 or lower Rev per mile factor. Then most of the time you need the TrueSpeed "black box" that does a translation of the speed pulses from the tone ring and sends the corrected pulses per minute to the PCM.
As stated above, the speedo will still read accurately with a re-gear on the SuperDuty trucks because Axle rotations are what is being sensed... all you have changed is drive shaft RPM per Axle RPM....
If you make the tires taller or shorter (attached to the Axle) then you need to re calibrate the PCM... Ford can change it over a fairly wide range but is limited to the various legitimate tire sizes that the Factory would ever supply up to around 34~35 inch diameter in the 601 Rev per mile range...if you install 36 or taller with a 580 or lower Rev per mile factor. Then most of the time you need the TrueSpeed "black box" that does a translation of the speed pulses from the tone ring and sends the corrected pulses per minute to the PCM.
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Originally Posted by ron86toy
I apologize on my statement.....I am used to the old school way reading off the trans
But resetting the PCM after a gear change is a must. Without that, and with an auto tranny, you'd be lucky not to get tranny error codes (OD light blinking).
WARNING - the exception to the rule about gears is the E-series. The E-series DO take the speed reading from the output shaft of the transmissions.
Which, in a bit of trivia, means that the E-series 4R100 (and PCM) can be used for V10 transplants
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