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Discussion Starter #1
So Ive heard the gearing in the differential is important for power and fuel economy. Can anyone explain this to me and/or tell me if I should be paying to have mine changed. I have an 08 CM 5.7L with a 6" procomp lift...20" wheels and 35s. Thanks in advance!
 

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Discussion Starter #2
Bump for response!
 

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It's harder for the engine to turn a taller tire with a given gear ratio. The final gear ratio is what gives the engine leverage to turn the wheels. The 4.30 ratio needs to be changed to 4.70, with 35" tires, to give the same mechanical leverage the 4.30 ratio had with stock 32" tires. Even if you could change to a 4.70 ratio, that wouldn't compensate for the extra weight of 20" wheels, the heavier 35" tires and the extra weight of the 6" lift components. With the taller tires and all that extra weight you may need something like a 5.30 (?) ratio to get back to the same mechanical performance as stock.:(
 

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Discussion Starter #5
It's harder for the engine to turn a taller tire with a given gear ratio. The final gear ratio is what gives the engine leverage to turn the wheels. The 4.30 ratio needs to be changed to 4.70, with 35" tires, to give the same mechanical leverage the 4.30 ratio had with stock 32" tires. Even if you could change to a 4.70 ratio, that wouldn't compensate for the extra weight of 20" wheels, the heavier 35" tires and the extra weight of the 6" lift components. With the taller tires and all that extra weight you may need something like a 5.30 (?) ratio to get back to the same mechanical performance as stock.:(
Thanks for the reply....are we talking an expensive mod? :rolleyes:
 

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Discussion Starter #7
Kind of do you have 2WD or 4WD. 4WD is twice the money
i have 4wd...maybe they will give me a discount if i promise not to use it :D
 

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Discussion Starter #9
Loose the front drive shaft. BAM 2WD :D :cool: :eek:
Actually i just hit a low gear with the 5.7L for a wheelie... only using 2 wheels on the ground! LOL :eek:
 

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then maybe you need a turning break :D
 

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Discussion Starter #13
What good is my $5k supercharger gonna be without proper $900 gearing! LMAO! Oh well.....I need do it! And yes I said "need!"
 

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They have 4.88 gear on the market now. I am thinking about putting in my 2018, the shop quote me about $2,300 for both front and rear.
 

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with 35's you dont need to re gear . YES you loose some power and mpg.

IF you spend big to re gear , one gets "most" of the performance back , but not all the mpg . The weight of each tire works against you , and the parasitic gearing loss of even lower gears.

In less words , your good with the 35's
 

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2018 TRD Sport with a 6" lift front, 4" Block in the rear and 35-12.5-20, bought it that way 2 months ago. Just took it on vacation driving on I-15 in Utah the engine was at 3200 rpm 95% of the time to keep it at 75-80 mph. The truck was loaded with stuff but not more than 1000 lbs, if re-gear to bring to power band back for the 5th and 6th speed, I am seriously thinking about it. Besides, this truck need to be able to tow too.
 
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