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Changing the gear ratio


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Has anyone thought about changing the gears in the front and rear differential in their 2010+ SHO? I was just chatting to my dad about it and thought about taking my car to a well known shop around here and getting a price and info on it. I figure it would definitely make our cars launch harder but may promote wheel spin and a shut down easier. What are thoughts on this one?

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If you do. Look at the Explorer. But do the math homework etc before pulling the trigger.

 

Final drive ratio (Explorer)

 

3.5L V6 3.16 (FWD) / 3.39 (4WD)

 

3.5L EcoBoost 3.16

 

Going from a non PP 2.77 to a 3.39. I would imagine you would notice that. But will the turbos like it..... The Flex has 3.65 final drive (AWD). That is way to crazy IMHO.

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If you do. Look at the Explorer. But do the math homework etc before pulling the trigger.

 

Final drive ratio (Explorer)

 

3.5L V6 3.16 (FWD) / 3.39 (4WD)

 

3.5L EcoBoost 3.16

 

Going from a non PP 2.77 to a 3.39. I would imagine you would notice that. But will the turbos like it..... The Flex has 3.65 final drive (AWD). That is way to crazy IMHO.

 

NOT TRUE... Flex EB engine has a 3.16 AWD Axle Ratio... Flex also has 255-45-20's vs the SHO's 245-45-20"s which changes the actual ratio...

 

I am running Conti DW 255-45-18's which raise my axle ratio to around 3.40... (29" vs 27" diameter) They are also much lighter. Stock weight -63 lbs ea. DW + wheels - 48 lbs ea. After 30K... 45 lbs ea!!!!!!!!

 

Tony... by increasing the size of your tires... you have effectively lowered your axle ratio to a smaller # than 2.73. Easy to calculate... Just look at the diameter of your new tires vs. the stock diameter, and adjust accordingly. Heaver, larger diameter tires, all equal SLOWER TIMES!!!!!!!

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NOT TRUE... Flex EB engine has a 3.16 AWD Axle Ratio... Flex also has 255-45-20's vs the SHO's 245-45-20"s which changes the actual ratio...

 

I am running Conti DW 255-45-18's which raise my axle ratio to around 3.40... (29" vs 27" diameter) They are also much lighter. Stock weight -63 lbs ea. DW + wheels - 48 lbs ea. After 30K... 45 lbs ea!!!!!!!!

 

Tony... by increasing the size of your tires... you have effectively lowered your axle ratio to a smaller # than 2.73. Easy to calculate... Just look at the diameter of your new tires vs. the stock diameter, and adjust accordingly. Heaver, larger diameter tires, all equal SLOWER TIMES!!!!!!!

 

Think again! ;) The Flex has a larger tire, In terms would effect the ratio the other way. Besides, That came right from Ford's own webiste. I just forgot to add (failed to specify) its for the NA 3.5L. :)

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Think again! ;) The Flex has a larger tire' date=' In terms would effect the ratio the other way. Besides, That came right from Ford's own webiste. I just forgot to add (failed to specify) its for the NA 3.5L. :)[/quote']

 

WHOA.....................................

 

OBVIOUSLY... Flex tires are larger, and that lowers the tire RPM's by about 1% or -.4 axle ratio at most.

 

Your post talked about the SHO... and then you quoted the Flex at 3.65. This is an EB site... ALL EB Flex have 3.16 ratio, and ALL EB Flex have 20" tires STOCK. SHO uses 20" & 19" STOCK - All 20's are the same size. Only one OE tire at 19" according to Tire Rack, and they are smaller.

 

EB Flex - stock 20" x 255-45 - 29.0" 3.16 Axle Ratio EB SHO 20" 245-45 Stock - 28.7" 3.16 Axle RatioPP 2.73 Axle Ratio NON PP. EB SHO 19" 255-45 Stock - 28.1" 2.73 Axle Ratio Tony's 2.73 Axle Ratio - 255-55-19" - 30.0"

 

Simple math can calculate the differences. Tire RPM is the true test when you are using the same gears.

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WHOA.....................................

 

OBVIOUSLY... Flex tires are larger, and that lowers the tire RPM's by about 1% or -.4 axle ratio at most.

 

Your post talked about the SHO... and then you quoted the Flex at 3.65. This is an EB site... ALL EB Flex have 3.16 ratio, and ALL EB Flex have 20" tires STOCK. SHO uses 20" & 19" STOCK - All 20's are the same size. Only one OE tire at 19" according to Tire Rack, and they are smaller.

 

EB Flex - stock 20" x 255-45 - 29.0" 3.16 Axle Ratio EB SHO 20" 245-45 Stock - 28.7" 3.16 Axle RatioPP 2.73 Axle Ratio NON PP. EB SHO 19" 255-45 Stock - 28.1" 2.73 Axle Ratio Tony's 2.73 Axle Ratio - 255-55-19" - 30.0"

 

Simple math can calculate the differences. Tire RPM is the true test when you are using the same gears.

 

I won't disagree with your thoughts at all. I know that a overall smaller tire will raise the final output at the wheel. But Ford does not factor it that way. It lists the actual drive ratio of the transmission and does not factor in the tire size. Thats all I was trying to say. By reading my above post I see how my point could be misunderstood. Sorry about that.

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I thought about getting a price and info from the guy, he put 355's in my 69 Chevelle and did a great job. I know the taller tires were not going to help any but they sure do look cool! The 45 series were just way too skinny and there was an ugly gap around the wheel well of empty space, now I can barely get my hand in there to scrub my inner fender wells when I wash it. I am just not one for lowering a car so I just adjusted the tire height.

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  • 2 months later...

Running a 28 inch tall tire on the gt500 with 4.10. Stock size is 27 inches. Should put me at a 3.95. Getting some lower profile tires could put you in the 325 to 330 range. if I was going to do that, I would look at going to a 19 or 18 inch wheel. Would not think traction would be an issue.

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