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Gear ratio

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Discussion Starter · #1 ·
Sorry to bring up old post but I am unable to find an answer that is complete yet. To start off I just purchased a Used :worship:worship:worship 2006 GT Mustang with 38K miles with 5 Speed:worship:worship:worship The car has 93 octane tune, C&L Intake, Flowmaster exhaust catback system with H-Pipe from American muscle, eibach lowering kit, and an underdrive pully. These are all the things that I can see but everyday I am learning a little more about the car.

Now to the Big question. The Stang has 20" Foose Nitrous wheels on her and I am questioning the rear end gear ratio. My nav has gps speed readings so I know my top speed was accurate. After opening the car up yesterday it topped out 4th gear at about 115-120 mph...... Without getting under the car what gear ratio would you guys assume I am running. 3.55's :nono: seems to be out possibly 3.73's but im thinking 4.10's
 

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First thing is you posted in the wrong section. This is the right place for your question:2005-2010 Mustang GT Tech Forum | AllFordMustangs.com

Second, you are still missing some information to answer your question. What size are your rear tires and what is your redline?

Assuming your rear tires are 285/30/20 and your redline is 6,500rpm, to top out in 4th(1:1) at 120mph would mean you have 4.30 rear gears.


Use this calculator to figure it out yourself.
http://www.f-body.org/gears/
 

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Discussion Starter · #3 ·
I noticed that and I am trying to figure out how to move my post redline is 6k tire size 255/35/20
 

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you need to look at the sticker on the dif cover, or rotate the tire 3 revs, and count how many revs the ds makes, and do the math, pretty easy, divide the ds revs by the 3. I think thats it, 23 years since I had to do that, lol
 

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Assuming your speedo is correct, if you're topping out 4th gear around 115 you most likely have 4.10 gears! There's a ton of different calculations out there that can help you figure out what gears are in your car.

I hope this helps! Please let me know if you have any questions or need some assistance. Our Mustang Experts are here Monday-Friday from 9AM-9PM EST and Saturdays from 9AM-5:30PM EST. If you want to hit them up, their number is 866.727.1266. I can also have one of them call you directly.

-Dan
 

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This is what I do, I either use this: Gear Calculator: Use Our Gear Calculator for Proper Gear Ratios or jack up the rear of the car and put the transmission in neutral so you can spin the rear tires. If you spin one tire and the other spins in the opposite direction, you have an open differential. In this case spin one tire in two complete rotations while watching the drive shaft. However many times the drive shaft spins per the two rotations of the tire, that's the ratio you have (if the drive shaft spins just over four times, you have 4.10's in there).

If you spin one tire and the other spins in the same direction, you have a limited slip differential. In this case everything is the same, the only difference is you spin the tire just one rotation. Hope this helps!
 

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BTW car looks badass:thumbup:
 

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Discussion Starter · #9 ·
Thanks guys I am in love with it! I have not had a mustang that runs in years! My foxbody that sits in the garage that needs a lot of body work. I sold my bike and replaced it with something that stays on 4 wheels instead of balanced on one!:kooky:
 
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