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Discussion Starter #1 (Edited)
I posted this in a different thread but want to start a thread about gears and ratios so that it will be easier to search for later!

stock tires 285/40/18 (tire height is 27 inches)
4.56 @ 65mph is 2324rpm with stock tires
4.10 @ 65mph is 2089rpm with stock tires
3.73 @ 65mph is 1901rpm with stock tires
3.31 @ 65mph is 1687rpm with stock tires
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Now with 305/35/20 (tire height is 28.4 inches)
3.31 @ 65mph is 1604rpm
3.73 @ 65mph is 1809rpm
4.10 @ 65mph is 1986rpm
4.56 @ 65mph is 2209rpm
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Top Speed @ 6000rpms in 6th gear
stock tires
4.56 = 167.9mph
4.10 = 186.7mph
3.73 = 205.1mph
3.31 = 231.1mph

now top speed with 20's
4.56 = 176.5mph
4.10 = 196.3mph
3.73 = 215.8mph
3.31 = 243.2mph

I used these calculator list in the previous post to come up with this info. The the calculators are correct why wouldn't you put 4.10's or maybe even 4.56's?

Face it driving down the highway with 4.10's @ 65mph @ less than 2100rpms is not bad and if you want to you can go almost 187mph in 6th gear (how often are you going to do that?) and if you put 20's on your rpm will lower because it is a taller tire. I think I will be putting 4.10's in eventually!

Here are the transmission gear ratios:
Gear ratios

1st 2.97

2nd 1.78

3rd 1.3

4th 1.0

5th .80

6th .63

calculators use:
http://www.miata.net/garage/tirecalc.html
http://www.csgnetwork.com/multirpmtirecalc.html
http://huntergraham.com/twcc.htm
 

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You need to look at the MPH at the top of 4th gear before you deside. You need to finish the quarter mile in 4th as there is no quick shift from 4th to 5th and you will slow down a bunch if you cannot finish in 4th. Figure your mph at the end of the quarter with your planned HP mods then find the gear that will put you just under that with your tires.

For stock size tires and up to about 550 RWHP, 4:10s are about optimum. With shorter tires or more HP, 3.90s or 3.73s become more appropriate. Its not just cruising RPMs that matter.
 

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JJ, this is great stuff man. You are on it as this will definitely answer a lot of people's questions. I'm staying with the 3.73s because Fred.................. told me to.

Thanks

flipmo
 

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Discussion Starter #4
I did this for most that are concerned about about driving on the street. but since you asked:

4th gear @ 6000rpms with stock tire size (27 inches)
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3.31 = 145.66 mph
3.73 = 129.26 mph
4.10 = 117.595mph
4.56 = 105.735mph

for all the drag racer!:D
 

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JJ nice leg work.This should definitely help people out.My opinion is that most of the people here are not drag racing much(but at times) and are more apt to be aggressive street drivers who also like to take trips on the freeway.This is just my opinion.

Jcthorne thanks for your input. I think this will help people out.
 

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Discussion Starter #6
JJ nice leg work.This should definitely help people out.My opinion is that most of the people here are not drag racing much(but at times) and are more apt to be aggressive street drivers who also like to take trips on the freeway.This is just my opinion.

Jcthorne thanks for your input. I think this will help people out.
NP.......It took a little time but I can refer back to it just as well as other can.
 

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Great info!

I've been mulling around thinking about upgrades - and thought I had been set on the 3.73 gears, but 4.10 may be better.

I drive the car every day. When you can violate the speed limit in 2nd gear, I think a lower gear set is in order. The GT500KR (by the way, anybody have one or see one yet?) is supposed to come with the 3.73.

Again, Thanks for the info - I think that I'm going to get a set of 4.10s instead of the 3.73s

RH
 

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Great info!

I've been mulling around thinking about upgrades - and thought I had been set on the 3.73 gears, but 4.10 may be better.

I drive the car every day. When you can violate the speed limit in 2nd gear, I think a lower gear set is in order. The GT500KR (by the way, anybody have one or see one yet?) is supposed to come with the 3.73.

Again, Thanks for the info - I think that I'm going to get a set of 4.10s instead of the 3.73s

RH
TrickyDick (Kool Nic), I was passionately considering switching again to the 4.10s, but I just didn't want the high revving while out on the interstate. Trips to Dayton and Detroit is preventing me from doing so but I do love the idea. If and when you swap, let us all know how you like the every day driving along with consistencies of RPMs around town and interstate.

Thanks

flip
 

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Kind Of Off-Topic Here..........But

I just couldn't resist with this "Nic" thing again. Well, we have on the board a MobeyDick, a TrickyDick, so to round it off I think it's only appropraite that I change my Nic to Super_ _ _ _. :D :D :D

flip
 

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Re: Kind Of Off-Topic Here..........But

I just couldn't resist with this "Nic" thing again. Well, we have on the board a MobeyDick, a TrickyDick, so to round it off I think it's only appropraite that I change my Nic to Super_ _ _ _. :D :D :D

flip
Now Now, only if your wife signs on and is willing to testify!!! :eek: :eek:

I too couldn't resist..........:rolleyes:
 

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If I were to change mine I would go with the 4:10 that's just me though.
 

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Question:
How much should gears cost to install?
I'm putting on the suspension and driveshaft this week, and want to get the gears in before the weekend (hoping the weekend is nice!!)

the stealership estimated $800. I asked a friend who works for american axel and he said around 400-500 at max. just want to get a heads up from guys who have had them installed. I'm going to make a call to a local speed shop and see how they can help me (alternative auto in Mount Clemens, MI).
 

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Question:
I'm going to make a call to a local speed shop and see how they can help me (alternative auto in Mount Clemens, MI).
If I were close enough, I would have Lidio and his crew do the install. Have them put the Whipple in, too.
 

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Yepper =) tis the plan!
 

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Discussion Starter #15
Question:
How much should gears cost to install?
I'm putting on the suspension and driveshaft this week, and want to get the gears in before the weekend (hoping the weekend is nice!!)

the stealership estimated $800. I asked a friend who works for american axel and he said around 400-500 at max. just want to get a heads up from guys who have had them installed. I'm going to make a call to a local speed shop and see how they can help me (alternative auto in Mount Clemens, MI).
yes about 400-500 is about right. the gears are 200-250 then about 200 for the instal.

JJ
 

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now that is just crazy!!
i've already purchased the gears and the dealership knew that.

sooooo they were charging 3.5-4 TIMES what they should have. alright, from now on i'm doing all my own work.
 

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I'm having 3.73's installed in a couple of weeks. Made the appointment today. :)
 

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I'm having 3.73's installed in a couple of weeks. Made the appointment today. :)
FYI. I drove 700 miles to evolution with stock gears and got 20 mpg.

On the way home with the 3.73 gear I got 19 mpg but I had a lot more weight in the car. Parts replaced at evolution.

With the stock gears at 74 mph I had 2000 rpm.

With the 3.73 gears at 74 mph I had 2250 rpm.

Hope that helps.

Cal
 
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