How to calibrate Speedo and Odometer for larger tires?

95cobby

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How did you guys with 37” or larger tires recalibrate your speedo and odometer for the larger tires? Right now truck is 3-4mph off at 70mph and at 10miles the gps will read 11 and some change.

I’ve tried using forscan to reprogram for 37s but it keeps giving me an error upon flash.

I’ve requested new tunes for 37s but all they did was change the shift points and not let the truck lag in higher gears.

Has anyone used the Hypertech thingy.. or anything else to get an accurate speedo/odometer?


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HossDieselWorks

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Im also wanting to know as well. Tried to also do use ForScan and keep getting an error message when I try to program. Returned my truck to stock before trying to program.

Only difference is mine is an 08 6.4 that has been d*****d using S p a r t a n.
 

Powerstroke Man 6.4

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Im also wanting to know as well. Tried to also do use ForScan and keep getting an error message when I try to program. Returned my truck to stock before trying to program.

Only difference is mine is an 08 6.4 that has been d*****d using S p a r t a n.

You can adjust tire size via ost options.
 

Powerstroke Man 6.4

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How did you guys with 37” or larger tires recalibrate your speedo and odometer for the larger tires? Right now truck is 3-4mph off at 70mph and at 10miles the gps will read 11 and some change.

I’ve tried using forscan to reprogram for 37s but it keeps giving me an error upon flash.

I’ve requested new tunes for 37s but all they did was change the shift points and not let the truck lag in higher gears.

Has anyone used the Hypertech thingy.. or anything else to get an accurate speedo/odometer?


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Ford has a software hard limit set a 34.5 inches

You can adjust for bigger tires above 34.5 inches with forscan via bcm as-built but you would have to live with a CEL and PCM/BCM mismatch code.
 

8WR_ZJ

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Hypertext speedo works flawlessly. We have had it on alot of trucks with 38 and 40 inch tires. Zero issues.

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95cobby

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Ford has a software hard limit set a 34.5 inches

You can adjust for bigger tires above 34.5 inches with forscan via bcm as-built but you would have to live with a CEL and PCM/BCM mismatch code.

I've tried several times with ForScan and kept getting an error "writing block 12 failed - incompatible configuration".

Do I have to return the truck to stock first?


Hypertext speedo works flawlessly. We have had it on alot of trucks with 38 and 40 inch tires. Zero issues.

Sent from my SAMSUNG-SM-G870A using Tapatalk

Good to know, thanks man
 
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I run the Hypertech speedo thingy with 37’s and according to the speed warning signs that post your speed it’s dead on.


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95cobby

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Just bought the Hypertech today.. from what I’ve read it connects to the ipc module and works regardless of tuner


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8WR_ZJ

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Yup exactly how it works.

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95cobby

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Took me all of 20 minutes to remove all the trim pieces, install this, and put it all back together. Works great! Don't forget to leave the usb cord plugged into it in case you need to make adjustments.
 

HossDieselWorks

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Not to hyjack the thread, but it also took me about the same to get everything done, installed and tested out. Works great on a 6.4 also! Just wanted to let others know as well.
 

mysticblu999

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I've got the inline module for my 37s. It works but ever since I installed it my "miles to empty" flashes every minute. You can leave the USB cord to where you can reach it, but I found it easier to put it in the middle of the range of my H&S Blackmaxx and fine tune from there.
 

BigRed97

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I've got the inline module for my 37s. It works but ever since I installed it my "miles to empty" flashes every minute. You can leave the USB cord to where you can reach it, but I found it easier to put it in the middle of the range of my H&S Blackmaxx and fine tune from there.

Ya know mine does that too, but I never could remember if it did it before or not
 

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