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Q: I'm rebuilding my engine.

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Engine Specs are going to be 685 HP and 680ft-lbs. I need to know what my gear ratio should be in the front an rear axles. For that power and torque. It's going to be a street / off road vehicle. Thanks for any help also my truck is 4x4
My car has an automatic transmission.

Depending on what you plan on doing with your vehicle for off road will determine what ratio you want. If you plan on going slow and rock climbing, then I recommend putting in a 4:56 gear ratio. If you plan on going fast but not too fast like 90 to 120 mph, then I recommend a 4:11 gear ratio. If you are planning on making your vehicle a desert off-road vehicle, then I recommend a 3:73 gear ratio. The higher the gear ratio number the slower the vehicle will go but there will be more power to the wheels. The lower the gear ratio number the faster the vehicle will go but will have less power to the wheels.

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