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3.73 ford 3.9l f150

  1. Axles & Differentials
    Big problem. I just had new gears put in my rear diff after doing some math on a gear calculator and asking for all of your opinions. My top speed is 65 mph at 2300rpm, not much more above 2300. I was running 4.10 before and got it up to 70 with them, but cant seem to get above 65 now, thought I...