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Author
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Topic: 4.30 gears?
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Impact 5.0
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Member # 2805
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posted
 
 
I was driving down the freeway last night in a 96 cobra I just bought and I noticed I was at 3,000 rpm at 80 mph in 5th gear, So I called a gear shop and they had some "tech sheet" on gears and they said with the size tires I am running 245/45R17 and the speed I was going I had 4.30 gears, does that sound about right?
Posts: 2173 | From: Tracy, CA | Registered: May 2003
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bunchmyfunky
CAFords Drag Racing Mod
Member # 360
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posted
I have the same size tires and turn 3k at 80mph on the stock tach and have 4.10s
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01 GT 5spd
1.76 12.79@105.49
Posts: 2433 | From: Vacaville | Registered: Jul 2001
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Unregistered
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Member # 786
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posted
It sounds like 4.10's to me.
Posts: 1785 | From: Livermore | Registered: Jan 2002
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Blu50Stang
CAFords OG
Member # 489
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posted
The gear calculator I used says 4.30s, however stock tachs aren't always accurate.
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Ross
'88 GT - 5.0&SF 4/04 | MM&FF 8/09 | MM&FF 79-93 Mustang Performance Cover 12/12
'17 GT350R
Posts: 1916 | From: Not CA | Registered: Oct 2001
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Stimson
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Member # 51
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posted
The RaceSystems Peformance Calculator software is good for this kind of stuff:
http://www.racesystems.com/perfcalc/
To use it to solve your problem, run the porgram and click tire/grear.
RPM= 3000
MPH = 80
Tire diameter = 26" (you really need to accurately measure this with a ruler yourself)
The gear ratio it'll give you is 2.9.
Remember this is the final drive gear ratio and:
Final drive gear ratio = rear end gear ratio X tranny gear ratio
In this case your tranny ratio is 0.67 in 5th gear so we have:
2.9 = rear end gear ratio X 0.67
thus
rear end gear ratio = 2.9 / 0.67
giving us
rear end gear ratio = 4.30
Now normally I would have just done the math and replied with a simple "4.30's if the numbers you gave me are correct" and not bothered revealing the secret to my mojo ![[Wink]](wink.gif)
Posts: 2373 | Registered: Jun 2000
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RO2USH
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Member # 2002
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posted
Suffice it to say, you don't have stock gears. I would say that you probably have 4.10's, but, like he said, Stock Tach's aren't always right. The only way you are really going to be able to tell is by opening up your diff, and counting the teeth. As long as your speedo is corrected for the gears, then I wouldn't worry too much about it.
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2002 Roush FR500
2004 Cobra
1965 GT 350 Clone
2003 Ducati 999
Posts: 286 | From: Sacramento | Registered: Oct 2002
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stoauto
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Member # 2803
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posted
aint no secret ![[patriot]](graemlins/patriot.gif)
[ November 06, 2003, 02:03 PM: Message edited by: stoauto ]
Posts: 1054 | Registered: May 2003
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Blu50Stang
CAFords OG
Member # 489
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posted
quote:
Originally posted by RO2USH:
The only way you are really going to be able to tell is by opening up your diff, and counting the teeth. As long as your speedo is corrected for the gears, then I wouldn't worry too much about it.
Opening the diff, counting teeth and dividing the #'s into each other is the only way of knowing for sure. If he doesn't want to do that, he can use the gear calculator and check it by getting under the car(jacked and supported by stands) and turning one of the rear wheels 1 complete rotation and counting how many revolutions the driveshaft makes(a little over 4 turns=4.10s a little over 4 and a quarter turns=4.30s).
[ November 06, 2003, 02:07 PM: Message edited by: Blu50Stang ]
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Ross
'88 GT - 5.0&SF 4/04 | MM&FF 8/09 | MM&FF 79-93 Mustang Performance Cover 12/12
'17 GT350R
Posts: 1916 | From: Not CA | Registered: Oct 2001
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Rev Happy
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Member # 661
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posted
You have 4.30s...
[ November 06, 2003, 05:09 PM: Message edited by: Rev Happy ]
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96 Cobra
Posts: 182 | From: Southern California | Registered: Dec 2001
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Impact 5.0
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Member # 2805
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posted
4.10 or 4.30--don't fear the gear right? Its got alot of balls off the line that all I have to say!
Posts: 2173 | From: Tracy, CA | Registered: May 2003
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Blu50Stang
CAFords OG
Member # 489
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posted
quote:
Originally posted by SteedaGT:
4.10 or 4.30--don't fear the gear right? Its got alot of balls off the line that all I have to say!
If you fear the gear, we can trade rear ends(your 4.whatevers for my 3.27s) ![[Big Grin]](biggrin.gif) ![[burnout]](graemlins/burnout.gif)
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Ross
'88 GT - 5.0&SF 4/04 | MM&FF 8/09 | MM&FF 79-93 Mustang Performance Cover 12/12
'17 GT350R
Posts: 1916 | From: Not CA | Registered: Oct 2001
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Impact 5.0
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Member # 2805
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posted
HA HA HA nope ![[Razz]](tongue.gif)
Also ross just ordered the steeda G-track suspension
[ November 06, 2003, 07:27 PM: Message edited by: SteedaGT ]
Posts: 2173 | From: Tracy, CA | Registered: May 2003
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