How to determine proper gear ratio
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New User
Joined: Dec 2004
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How to determine proper gear ratio
This is the first truck I've customized and never had reason to consider gear ratios in the past.
My new FX4 has a 6" lift, 20" wheels and Toyo Open Country tires 325/60/R20. I notice that without towing a load but in overdrive, going up even small hills cause it to downshift. Towing a 2500lb trailer but without overdrive on, going up even slight grades or even flat roads will cause it to downshift. The dealer told me that upgrading to larger tires would affect gas milage, but didn't mention any issues with towing.
In this forum I have read a number of threads about people changing the gear ratio. How do I know if that would help my situation? If it would, how would I determine the proper ratio? I currently have a 3:55 according to the paperwork that came with the truck.
Any advice?
My new FX4 has a 6" lift, 20" wheels and Toyo Open Country tires 325/60/R20. I notice that without towing a load but in overdrive, going up even small hills cause it to downshift. Towing a 2500lb trailer but without overdrive on, going up even slight grades or even flat roads will cause it to downshift. The dealer told me that upgrading to larger tires would affect gas milage, but didn't mention any issues with towing.
In this forum I have read a number of threads about people changing the gear ratio. How do I know if that would help my situation? If it would, how would I determine the proper ratio? I currently have a 3:55 according to the paperwork that came with the truck.
Any advice?
Junior User
Joined: Sep 2004
Posts: 66
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With your set up, gears would definitely help. What you want to do is keep the same effective ratio after your mods. When you increase tire size, it changes things and effectively makes the truck work harder to get going. Doa search on the internet for gear ratio calculator to get an idea of where you were originlly, where you are now, and what you need to change to to bring it all back together. 4 wheel parts may have one. Talking to a drivel line shop like Randy's Ring andPinion would also be a good idea.
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Joined: Oct 2002
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