07 Mustang GT - Custom Tune - Speedo Out

[TMBRoush]

I can't get my speedo calibrated

I have a 2007 Mustang GT - Canadian Car
U7145 with update R805
I had a custom tune done by an authorized dealer - Brown Bros Ford

I have a BBK CAI & BBK TB.
I Have a Stage 2 Roush set up with the axle back Roush Exhaust
After the Custom dyno tune I have 289.2 to the rear wheels
I have a Pioneer navigation system with AVG-1 Module

When the AVG shows my speed at 80KPH my car Speedo says 100KMH
(Before the tune they were the same)

I have 235/50/18 Ford upgrade wheels, I used the formula in the instruction
20168 divded by wheel Diameter 27.25 Inches = 740 Rev per Mile

I changed the REV Per mile from 771 to 740 on the custom tune and the speedo numbers didn't really change after reinstalling the modified parameter

Brown Bros said they can try reflashing my custom tune with the new REV Per mile numbers and see if that helps

Any suggestions?

Thanks
Travis

[TMBRoush]

It appears that the custom tune changed my gears to 3.29? so I went in and changed to 3.54 option. I thought that the 2007 mustangs had 3.31 for automatic and 3.55 for manual from the factory.

Anyhow I test drove the car after changing the parameters and my Speedo is now correct.

[mikel]

Sweet!