Power Hungry Performance Forum - Speedo/Odo correction

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- - Speedo/Odo correction (http://forum.gopowerhungry.com/showthread.php?t=891)

orygunf150

Sat, April 4th, 2009 01:52 PM

Speedo/Odo correction

Reading this thread
http://www.ford-trucks.com/forums/836709-odo.html
I am also wondering, does changing the tire size on our programmer also change the Ford speedo or just the programmer? My Ford speedo is a few mph off but the Gryphon reads about right, (according to my GPS).

Sburn

Sat, April 4th, 2009 02:04 PM

Quote:

Originally Posted by orygunf150 (Post 7193)

If your Gryphon matches your GPS, you're fine. Odo will also be correct. Your speedo will be 3% higher than your actual (GPS) speed because Ford set it that way.

Jackpine

Sun, April 5th, 2009 12:19 AM

Quote:

Originally Posted by Sburn (Post 7195)

If your Gryphon matches your GPS, you're fine. Odo will also be correct. Your speedo will be 3% higher than your actual (GPS) speed because Ford set it that way.

Very good, Sburn! I hadn't thought of the speed difference in terms of percentages. :doh: That explains why it's only about 1 mph fast in the 40 mph range and is 2 mph fast in the 70 mph range.

And, back to the OP's question - yes! Programming the PCM with a new tire size set in the programmer DOES change the dashboard speedometer too. The PCM controls the speedometer readout in the new trucks.

- Jack

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