GT Performance Mods 2005+ Mustang GT Performance and Technical Information

Speedo Calibration

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Old 8/20/05 | 10:19 PM
  #1  
Fman67's Avatar
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Joined: November 22, 2004
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:bang: Hello everyone...have a question. I have changed gears,and i have Predator with r22. Trying to get my speedometer exact. I have gone through tuner and made adjustments...but no matter what i do...i am 5-7 mph off. Speedo reads faster than i am actually going. Any ideas. I have 3.73's with 255/50/17's. Thanks!
Old 8/20/05 | 10:32 PM
  #2  
Stang281's Avatar
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Joined: November 11, 2004
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From: South Georgia
It did this on my Dad's '03 Silverado 6.6

We can't figure out why it isn't adjusting the speedo properly...it's ~13mph off and he was pulled over today because of it, so we've got to figure something out soon. (luckily he only got a warning though) We made the tire adjustments, that was it as far as custom adjustments, and it isn't right.
Old 8/20/05 | 11:13 PM
  #3  
don_w's Avatar
 
Joined: June 21, 2005
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Originally posted by Fman67@August 20, 2005, 9:22 PM
:bang: Hello everyone...have a question. I have changed gears,and i have Predator with r22. Trying to get my speedometer exact. I have gone through tuner and made adjustments...but no matter what i do...i am 5-7 mph off. Speedo reads faster than i am actually going. Any ideas. I have 3.73's with 255/50/17's. Thanks!
How many revs per mile did you enter for tire size? By my calcs, it should be about 746. Also, is the Predator correctly set for manual or automatic trans?
Old 8/21/05 | 05:11 AM
  #4  
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Joined: November 29, 2004
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Fidele just asking and trying to help - you changed the gear ratio in the modify tune menu, then saved those changes, then reinstalled the custom tune with the changes - correct?? You should not need to correct for tire size. You have the same size tire as I do and it is within .1 of the diameter as the original tires - that's another reason I chose that size tire.

The current software for the U7140 Predator is r23. However, I don't know what has been improved in the new version so I wouldn't automatically update the tool.

PS: why not 4.10 gears?
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