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Old 03-10-2012, 01:48 PM
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Tire size and diff ratio questions

Stock is 245/75 R17 and I have a 3:73 diff. If I go to a 8" lift with 37x13.50x24 toyo tires will it act like I have a 3:55 diff or close too it or how does that calculate? I know it will will affect my speedometer but I'm looking for numbers on how it will act for towing ect. Thanks guys
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Old 03-11-2012, 01:59 AM
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Watch out for nosebleeds up there! Seriously, I don't have clue Bud as I have not gone down this path as of now, good luck.
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Old 03-11-2012, 09:44 AM
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Matty. Check this website. You can plug and play the gear ratios and tire heights and see if it's in the recommended RPM range. Calculators

I'm running 3:55s with 37x13.50s. Towing an enclosed trailer of about 7000lbs at 105km/h my RPM is roughly 1400-1500. Fuel mileage of about 11mpg. All hand calculated from Vegreville AB driving the Yellowhead to Valemount BC. Im sure it's the mountain driving that really kills mileage
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Old 03-11-2012, 06:01 PM
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At 100 km I'm running around 1850-1900 rpm with the stock wheels, I'm suRe that will drop with bigger tires, less revs per mile . I'm guessing
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Old 03-11-2012, 06:39 PM
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Quote:
Originally Posted by matty21 View Post
At 100 km I'm running around 1850-1900 rpm with the stock wheels, I'm suRe that will drop with bigger tires, less revs per mile . I'm guessing
Hey Matty, i believe with 37's you should be about 1650-1750rpms. i may be wrong but i think that will be close.
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Old 03-11-2012, 07:57 PM
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Axle Ratio - B&C Offroad

I have always used this site for my gear ratio questions, but If I am correct, your stock is a 31.5" and going to a 37" It will be like having 3.18 gear ratio
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Old 03-12-2012, 02:53 AM
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Thanks guys
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Old 03-12-2012, 11:25 AM
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So when you doin the Lift Matty?? Once it's done we'll have to meet up for a beer and take some pics of our black beauties together haha
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Old 03-12-2012, 11:34 AM
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stupid question but what does the RPM "you should be at" mean? I assume for optimal driving MPG's...

I had 255's on my silverado then went to 285's and the rear diff gear ratio kills me on gas. Always wondered what I should have done to fix it. Figured you guys would know.
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Old 03-13-2012, 03:35 AM
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Originally Posted by AlbertaStroker View Post
So when you doin the Lift Matty?? Once it's done we'll have to meet up for a beer and take some pics of our black beauties together haha
Sometime soon, that would be cool!
Quote:
Originally Posted by TX_TRU_STUD View Post
stupid question but what does the RPM "you should be at" mean? I assume for optimal driving MPG's...

I had 255's on my silverado then went to 285's and the rear diff gear ratio kills me on gas. Always wondered what I should have done to fix it. Figured you guys would know.
255 to 285's that's just a Width change that wont do anything but add weight, it's the profile that will change the ratio, maybe because it was a gm. Lol and a gasser.
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