01 Gt Gear Ratio

Discussion in 'SN95 4.6L Mustang Tech' started by Paul1981610, May 24, 2014.

  1. Paul1981610

    Paul1981610 Member

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    Just purchased 01 gt. Noticed the speedo off by 5-6 at 75 mph. Checked under car it has a chrome diff cover. So I assume different gears. I jacked the car up just the passenger and the driveshaft only turned a little over two times per the one tire rotation. That can't be right. Oh and the speedo is reading fast not slow what gear ratio. It runs 2100 at 75-80 mph
     
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  2. Three50won

    Three50won Member

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    What trans is in it? Auto or manual? Also, do you know if it is the stock trans? Here is a little info:

    3.27 - At 75 MPH if you have a tremec 3650 trans then your RPMs will be around 2100. If you have an auto then you will be at around 65-70 MPH at 2100 RPMs.

    3.55 - At about 70 MPH with a tremec 3650 trans your RPMs will be 2100. WIth an auto trans at 2100 RPMs your speed will be around a little over 60 MPH.

    This is all if you have the stock tires on the car and of course the stock trans.
     
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  3. Paul1981610

    Paul1981610 Member

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  4. Paul1981610

    Paul1981610 Member

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    T3650 w/ 245/45/17. The whole driveshaft count is what is confusing me. There's no way it has 2:25. To quick to many rpm at hwy speed
     
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  5. Three50won

    Three50won Member

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    So you have 3.27s then. Maybe you counted the driveshaft or the tire revolutions incorrectly. But yea according to your 5th gear speed and RPMs you have 3.27.
     
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  6. Paul1981610

    Paul1981610 Member

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    Just finding that hard to believe with speedo off. And I did the driveshaft rotation three times to make sure I counted right.
     
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  7. Three50won

    Three50won Member

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    Your speedo is not off. If you have the tremec, and you're at about 75 mph, then your RPMs should be right where they are...at about 2100 with 3.27s. Perhaps they were swapped out and then the stock ones were re-installed. A better way to check might be to set your cruise control to 60 mph and monitor your trip odometer while timing yourself. If it takes a minute to travel one mile then your speedometer is correct.
     
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  8. Paul1981610

    Paul1981610 Member

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    GPS has me off by 5. Maybe the gears have been out back to original but speedo is off
     
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  9. Three50won

    Three50won Member

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    Do a manual check of your speed without using GPS. For all you know the GPS could be off. Like I said, drive at 60 while carefully monitoring your trip odometer and a 60 second timer. That is your best bet and the only truly accurate way to know for sure. And while you're at it, note the exact RPMs at 60 mph in 5th gear. After all that let me know and I'll figure it out for ya.
     
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