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  • SN95 4.6L Mustang Tech

3:73 gears

  • Thread starter Thread starter 03stang0289
  • Start date Start date Jan 27, 2010
0

03stang0289

New Member
Jan 22, 2010
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Jan 27, 2010
#1
  • Jan 27, 2010
  • #1
i have an 03 5speed gt. Im putting in 3:73 gears . what will my rpm be on the highway at 65 mph? it runs at about 1500 rpm at 65mph now. what will it go up to?
 

Sonic04GT

Member
Nov 1, 2009
844
2
19
West Palm Beach, FL
Jan 27, 2010
#2
  • Jan 27, 2010
  • #2
What size rear tires do you have? There are different factors that play into this.

For example, I run 295/35/18:

MPH = 65
Tire Diameter = 26.12
Rear Gear Ratio = 3.73:1
Trans Gear Ratio = .68:1 (5th gear, 1:1 for 4th)
So in theory I would be at 2120.79 RPMs

Someone feel free to chime in if my figures are incorrect.
 
0

03stang0289

New Member
Jan 22, 2010
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Jan 27, 2010
#3
  • Jan 27, 2010
  • #3
stock 275 45 17 . is that your car in the pic? i like the color!
 
P

peepeeskillz

New Member
Mar 23, 2009
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texas
Jan 27, 2010
#4
  • Jan 27, 2010
  • #4
with 4.10s im at about 2k at 60mph, so 3.73s should be less maybe 1700-1800?
 
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03stang0289

New Member
Jan 22, 2010
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Jan 27, 2010
#5
  • Jan 27, 2010
  • #5
how do you like the 4;10 on the highway? i get on the highway pretty often so i went with the 3:73 wondering if i should have went with 4:10
 

Sonic04GT

Member
Nov 1, 2009
844
2
19
West Palm Beach, FL
Jan 28, 2010
#6
  • Jan 28, 2010
  • #6
03stang0289 said:
stock 275 45 17 . is that your car in the pic? i like the color!
Click to expand...

With a 275/45/17 tire, theoretically you should be at...

2072 RPMs in 5th gear

or

2344 RPMs in 4th gear @ 50mph
 

sneaky98gt

10 Year Member
Apr 23, 2008
2,387
144
114
NC State University
Jan 28, 2010
#7
  • Jan 28, 2010
  • #7
peepeeskillz said:
with 4.10s im at about 2k at 60mph, so 3.73s should be less maybe 1700-1800?
Click to expand...

Dang, is there that big of a difference in the stick and auto tranny overdrives? I'm a bit over 1800 at 60 and I have the stock 3.27s....
 
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peepeeskillz

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Mar 23, 2009
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texas
Jan 28, 2010
#8
  • Jan 28, 2010
  • #8
sneaky98gt said:
Dang, is there that big of a difference in the stick and auto tranny overdrives? I'm a bit over 1800 at 60 and I have the stock 3.27s....
Click to expand...

with stock 3.27s i was at 1550 at 60mph thats with a TR3650 trans tho, 01 and older cars are different.

and on the highway its not that bad at 80mph its at about 2700, doesnt seem that high since my old car, and both my moms and my sisters car are at or over 3000 at 80.
 

03ghoststang

Well-Known Member
Jul 16, 2005
1,930
1
57
Los Angeles, California
Jan 28, 2010
#9
  • Jan 28, 2010
  • #9
well if u are planning on doing future mods and/or considering a S/C then go with what will benefit u later..............but if staying N/A then 4.10's not that bad if you stay off the throttle
 

ChillPhatCat

20+ Year Stangneter
Apr 22, 2002
409
65
48
Syracuse, NY
Jan 28, 2010
#10
  • Jan 28, 2010
  • #10
peepeeskillz said:
with stock 3.27s i was at 1550 at 60mph thats with a TR3650 trans tho, 01 and older cars are different.

and on the highway its not that bad at 80mph its at about 2700, doesnt seem that high since my old car, and both my moms and my sisters car are at or over 3000 at 80.
Click to expand...

But they're driving 4 bangers no? V8's are more intended to cruise around 2k whereas 4cy's are designed to cruise around 3k rpm. Not saying it's harmful, it's just not where they're terribly efficient. Obviously a higher gear ratio will hurt gas mileage no matter the car.
 

midnightdriver

Active Member
Jan 3, 2010
443
2
27
Northern California
Jan 28, 2010
#11
  • Jan 28, 2010
  • #11
I had 3.73's in my 85 K5 blazer with the turbo 400 trans and my rpms were about 2800 at 75 mph. It didn't seem to mind it, just sounded like you needed another gear.
 
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peepeeskillz

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Mar 23, 2009
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texas
Jan 28, 2010
#12
  • Jan 28, 2010
  • #12
ChillPhatCat said:
But they're driving 4 bangers no? V8's are more intended to cruise around 2k whereas 4cy's are designed to cruise around 3k rpm. Not saying it's harmful, it's just not where they're terribly efficient. Obviously a higher gear ratio will hurt gas mileage no matter the car.
Click to expand...

yea my sisters car is a 4 banger integra, but my moms car has a v6. my old car was an old 94 LS400 with a 4.0 v8 and it was about the same rpm as i am right now with 4.10s, but it did have an auto

i do notice having to give it more gas with 4.10s at highway speed compared to 3.27s just to cruise, but i dont know how much my mileage is actually effect since i dont do alot of highway driving, in the city so far my mileage was the same as 3.27s
 

Tanus

New Member
Dec 11, 2009
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A to the Z
Jan 28, 2010
#13
  • Jan 28, 2010
  • #13
I think 4.10s are perfect, on the highway at like cruising speed @ 70mph, rpms are at like 2k. I dont think it affects mpg much either, my car gets 15mpg (city) with aggresive driving and my car runs low 12s too
 

ChillPhatCat

20+ Year Stangneter
Apr 22, 2002
409
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Syracuse, NY
Jan 28, 2010
#14
  • Jan 28, 2010
  • #14
peepeeskillz said:
in the city so far my mileage was the same as 3.27s
Click to expand...

Yeah I can see that, you have more options for gears in the city than out on the highway, you just shift sooner. On the highway you "run out" of gear more or less.
 

deftsound

Please ask me how much my supercharger cost
Apr 6, 2004
945
1
39
Texas City TX
Jan 29, 2010
#15
  • Jan 29, 2010
  • #15
I have 3.73's and love them, but if i was N/A I would have gone with 4.10's.
 

Rickyll7

Member
Dec 16, 2005
718
4
19
Jan 29, 2010
#16
  • Jan 29, 2010
  • #16
Tanus said:
I think 4.10s are perfect, on the highway at like cruising speed @ 70mph, rpms are at like 2k. I dont think it affects mpg much either, my car gets 15mpg (city) with aggresive driving and my car runs low 12s too
Click to expand...

How in the world were you at 2k rpm with 4.10s at 70 mph? do you have a T56 and a 0.50 6th gear?

Gear Ratio Calc

If your turning 2k rpm at 70 mph with stock height tires and a stock tranny, you have stock 3.27 gears.
 

Tanus

New Member
Dec 11, 2009
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#17
  • Jan 29, 2010
  • #17
2k was just an estamate, its definatly under 2,500. I have a really tall rear tire too.
 

Rickyll7

Member
Dec 16, 2005
718
4
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Jan 29, 2010
#18
  • Jan 29, 2010
  • #18
Tanus said:
2k was just an estamate, its definatly under 2,500. I have a really tall rear tire too.
Click to expand...

What is the size of your rear tire?

Even with 275/50/17 tires, you would be over 2300 rpm.

Those tires would look ridiculous by the way.
 

Tanus

New Member
Dec 11, 2009
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Jan 29, 2010
#19
  • Jan 29, 2010
  • #19
275/60/15, really tall!

there's a pic in this thread, i like the way the look, just ignore the ****ty 10hole wheels, haha

http://www.stangnet.com/mustang-forums/805041-will-these-fit-295-65r15-bfg-drag-radials-93-fox.html
 

Rickyll7

Member
Dec 16, 2005
718
4
19
Jan 29, 2010
#20
  • Jan 29, 2010
  • #20
Tanus said:
275/60/15, really tall!

there's a pic in this thread, i like the way the look, just ignore the ****ty 10hole wheels, haha

http://www.stangnet.com/mustang-forums/805041-will-these-fit-295-65r15-bfg-drag-radials-93-fox.html
Click to expand...

That puts you at just over 2300 rpm at 70 in 5th.
 
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