Going from a 4.11 to a 4.88 gear ratio what should I expect the differences in torque and top speed to be? What about a 4.11 to a 5.13? And Finally a 4.11 to a 3.73?

Not sure about the torque. You'll have to figure this all out mathematically based on your current numbers and go from there. Here is a good link for figuring speed and what tire sizes are suitable to use on your vehicle.

Performance calculators For Your Modded Mustang

Keep in mind that even though this is for mustangs, it works the same for any vehicle. Your final tire size will also affect performance as your vehicle was designed to run a specific size and differing from that size by more than 3% may have an adverse affect on handling as well as other things. Good luck.

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