a 275/40/19 is a 27 inch tall tire and if you are at 2500rpm at 70mph, you sir have 4.30s gears. Its actually 70.3. Your tires are the wrong size for a Mustang. Are they drag radials?Ok. Correction. 275/40/19
A 35 series 19inch is 26.5" and a 30 series is 25.5". Stock is 25.68".
Mine for reference:
3.90 gears, 275/35/r18 is a 25 inch tall tire and at 2500rpm, Im at 71.7mph
stock: 3.27 gear 245/45/r17 is a 25 inch tall tire and at 2500 rpm, its at 85.9mph.
Axle calc for your use.
https://drive.google.com/open?id=0BxRmaQKbPZklMW54QXgwRmlzOUU
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