This is topic 4.30 gears? in forum Tech Talk at Northern California Ford Owners  .


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Posted by SteedaGT (Member # 2805) on :
 
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?
 
Posted by bunchmyfunky (Member # 360) on :
 
I have the same size tires and turn 3k at 80mph on the stock tach and have 4.10s
 
Posted by 04ParksRider (Member # 786) on :
 
It sounds like 4.10's to me.
 
Posted by Blu50Stang (Member # 489) on :
 
The gear calculator I used says 4.30s, however stock tachs aren't always accurate.
 
Posted by st5150 (Member # 51) on :
 
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]
 
Posted by RO2USH (Member # 2002) on :
 
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.
 
Posted by stoauto (Member # 2803) on :
 
aint no secret [patriot]

[ November 06, 2003, 02:03 PM: Message edited by: stoauto ]
 
Posted by Blu50Stang (Member # 489) on :
 
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 ]
 
Posted by Rev Happy (Member # 661) on :
 
You have 4.30s...

[ November 06, 2003, 05:09 PM: Message edited by: Rev Happy ]
 
Posted by SteedaGT (Member # 2805) on :
 
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!
 
Posted by Blu50Stang (Member # 489) on :
 
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] [burnout] [burnout] [burnout]
 
Posted by SteedaGT (Member # 2805) on :
 
HA HA HA nope [Razz]

Also ross just ordered the steeda G-track suspension

[ November 06, 2003, 07:27 PM: Message edited by: SteedaGT ]
 




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