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MMM JELLO!!!
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Discussion Starter #1 (Edited)
03 gt
manual
magnaflows
Mods that will go with gears:
K&N CAI
X Pipe
75mm throttle body
c&l Plenum
and tune
which gear will be good to go with IF in a year i will add a intercooled Supercharger?
 

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Banned from AFM member!
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It doesn't matter because if in a year you add an intercooled supercharger, you will need a custom tune regardless.
 

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lol the thread asks which gear, but you ask what tune? You'll need to be put on a dyno if you get a supercharger. as for gears, it really depends...there's a million gear threads on here where people ask what gears are best for their combo
 

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US Air Force (retired)
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Because of your plans to go FI, I would suggest 3.73s.
 

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3.73s, doesnt do bad NA and be perfect for power adder. 4.10s if you stay NA, they say its a world of difference between the 2
 

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just what i read buddy, i have 3.73s never had 4.10s
 

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I love my 3.73's. N/A for now and leave room for expansion. Fourth gear is great on the street and second and third work perfect for the track.
 

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MMM JELLO!!!
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Discussion Starter #13
my bad my bad i meant gear not tune lol. idky i put tune my mistake. whats the BIG difference between 3.73 and 4.10?
 

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Track times wont show a hole lot of diff between 3.73's and 4.10's. Some people think that their butt dyno is more accurate than times at the track. What will really slow you down is running out of gear at the track. Now if you plan on running a 28 inch tire with 4.10's and forced induction you may be ok but most guys who can drive good at the track with 400 rwhp can typicaly hit 116-118 mph which would be really streaching your motors legs in the rpms with a 26 inch tall tire.
 

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my bad my bad i meant gear not tune lol. idky i put tune my mistake. whats the BIG difference between 3.73 and 4.10?
A torque multiplier ratio of .37.

I can't remember if the late model TR3650's come with a first gear of 3.38 or 3.77. We'll pretend 3.38 to make us clear on the math.

So, in first gear, with 3.73's, at 4000 RPM's on a stock engine, your wheels are seeing a torque of 3,788 lb ft. With 4.10's, your wheels are seeing 4,157 lb ft.


That's the difference. You spin through your RPM's faster, and put more torque to the rear wheels.
 

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A torque multiplier ratio of .37.

I can't remember if the late model TR3650's come with a first gear of 3.38 or 3.77. We'll pretend 3.38 to make us clear on the math.

So, in first gear, with 3.73's, at 4000 RPM's on a stock engine, your wheels are seeing a torque of 3,788 lb ft. With 4.10's, your wheels are seeing 4,157 lb ft.


That's the difference. You spin through your RPM's faster, and put more torque to the rear wheels.
I don't know how your doing that math but that is alot of torque and I don't think that a dyno would spit out that number
 

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Gears are torque multipliers.


If you have a gear ratio of 3:1, for every 3 spins of the input shaft, your output shaft spins once. While your output RPM's are 1/3 of the input RPM, you increase the torque output by 3 times. This means that you will soon run out of revs, have to shift to another gear, and repeat this process, matching torque to desired speed of travel.

So, the flywheel spins at 4000 RPM, and you make 300 lb ft of torque at this rpm. Your first gear ratio is 3.38. This means that your torque at the output shaft of the transmission is now (300*3.38) 1,014 lb ft. Your RPM's are approximately 1,183 at the output shaft.

This is the speed of the driveshaft, which goes to another gear system (the rear differential). This has the same effect, and your lb ft. is amplified to (1014*4.10) 4,157 lb ft. Your RPM's are further reduced to 288 RPM's, which is the revolutions of your axles and thus your wheel/tire combination.

So, on a stock engine at peak torque RPM's, your wheels see this torque for the given gear with 4.10's

1(300*3.38*4.10) = 4,157 lb ft
2(300*2*4.10) = 2,460 lb ft
3(300*1.31*4.10) = 1,611 lb ft
4(300*1*4.10) = 1,230 lb ft
5(300*0.67*4.10) = 824.1 lb ft

You should see the obvious reduction of lb ft as you row through the gears - which also incidentally explains the reduction of acceleration as you slam through the gates, while you travel at a faster road speed. Make sense?

If the tires saw 4,157 lb ft of torque when you are in 5th gear at 3000 engine RPM's - I would absolutely agree with you. However, that simply isn't the case.

Dynos however are designed to calculate engine output. They do this by reversing the math through the gears and tire height, along with the pace of acceleration of the drums and the speed of the drums that the tires sit on.
 

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Shake N' Bake
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go with either, if you don't like one get the other

i run 4.10s with my nitrous and the only thing i need are tires that will ****in grab! :lol
 

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I'll throw in something new: 3.90's

Especially if your stuck between 3.73's or 4.10's. 3.90's will be fine with running the setup your looking into OP.
 

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US Air Force (retired)
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Gears are torque multipliers.

4(300*1*4.10) = 1,230 lb ft
QUOTE]

I need to see your references for these calculations. Almost all of our cars have been on chassis dynos which measure torque at the wheels and none of our cars make 1,230 lbs of torque.

Edit: I found the formula and saw your comment about dynos reversing the math. I find it interesting that I've never been asked by the dyno operator what my tire size or gear ratio was.
 
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