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Old 5/16/10, 4:12 AM   #1
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Gear ratio?

I am wondering how much of a difference would I notice if I went with the optional 3.73s or 3.55s vs. the stock 3.31 rear, in terms of acceleration? I guess the question I have is, if you lined then up side by side and raced 0-60 and 1/4 mile who would win and by how much?
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Old 5/16/10, 6:04 AM   #2
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There seems to be much debate on this at the moment.

More data needs to be presented to arrive at an answer on which gears will ET the best with the stock engine. Convention would say the 3.73. 3.73 will give the best seat of the pants around town feeling for sure.

Best way is to line 'em up and do it!
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Old 5/16/10, 7:42 AM   #3
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The seat of the pants feel, I will definitely agree with. When I drove a 10' GT w/3.31 and then another w/3.73 and they felt worlds apart. However, yestaerday, I drove an 11' w/3.31 and although it wasn't like wow around town, the 412hp definitely helped it feel faster, plus it seemed to make the 1-2 shift easier because there wasn't that thrust you get with the 3.73. I just would want to a sure myself that if an 11' w/3.73 lined up next to me, I wasn't about to get my *** handed to me.
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Old 5/16/10, 8:19 AM   #4
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Well I cant actually say. I can say stock you will run out or rpm in 4th with the 3.73. 6700-7000 rpm with 3.55. 6200-6500 rpm with 3.31. That if you dont live at high altitude.

My personal opinion is that 3.55 will be something less then a 1/10 quicker than 3.31 on a really well prepped track and 3.73 will be no quicker than 3.55. Thats on factory tires of course. Given stickies and different tire heights that all goes out the window. Evolution is running 3.73 to a 118 mph trap with tall slicks and a bumped rpm limiter for instance.

My personal car: 5.0 M6 3.55
Traction Control Off / Stability Control Off
20-30 MPH in 1st.
Nail Throttle
1-2 Shift (Car Goes a little Sideways)
Have to be on your game here. 2nd disappears in a hurry.
2-3 Shift (Barks 3rd Hard)

Did this a few times and although the tire spin in 1st from a 20-30 mph kick wasnt obvious the rubber coated rear fenders made it obvious it was spinning. So far I am not disappointed with my gear choice.
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Last edited by Gene K; 5/16/10 at 8:21 AM.
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Old 5/16/10, 8:52 AM   #5
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Though I'd still like to try 3.73s, its hard to disagree with the above.

Question for you Gene. How is the MT82? I know you just got your car, but does it feel like it can be aggressively shifted? Can you tell if the 4/5 gear can be shifted like the 2/3?

Would you mind pulling the tranny out and taking it apart to see if 5th is on the main shaft?

And congrats on getting your car - very jealous!
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Old 5/16/10, 10:57 AM   #6
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Sounds like the 3.73 is a minimal gain over 3.31. Looks like I may just get the 11' GT w/3.31 that's sitting on my dealers lot.
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Old 5/16/10, 12:19 PM   #7
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You can think of it like this: Bigger axles mean more acceleration but less top speed. There is also a penalty to gas mileage (but who owns a Mustang GT and thinks about that ) for bigger axles, simply because it takes more RPM to maintain a given speed in a given gear than a smaller axle (like the 3.31). It's not going to be a ridiculous difference mind since you also have to take the transmission and wheels into account. The main problem with the 3.73s seems to be that you either hit the rev limiter in 4th gear for the last hundred feet or so as someone pointed out, or you have to shift to 5th, and either will reduce the overall effect of the 3.73 axle compared to the other axles, but some think that maybe this can be corrected for.

This is all theory though. What we really need is someone to get their hands on all three.
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Old 5/16/10, 12:54 PM   #8
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Quote:
Originally Posted by jeff s View Post
There seems to be much debate on this at the moment.

More data needs to be presented to arrive at an answer on which gears will ET the best with the stock engine. Convention would say the 3.73. 3.73 will give the best seat of the pants around town feeling for sure.

Best way is to line 'em up and do it!
Yeah I was under the impression that Ford bumped the Bullitt to 6500 for its 3.73's with the 4.6/5 spd for best time/max spd in 3rd. (05-09 GT's were 6250) Didn't lose time shifting to 4th.

But with the new 6 spd that's all changed. 3.73's may not be the best in the 1/4 for the 5.0.

Though they may still be sweet for 2 lane twisties.
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Old 5/16/10, 1:24 PM   #9
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Yeah I was under the impression that Ford used the 3.73's for the 4.6/5 spd for best time/max spd (without hitting the 6500 limiter) in 3rd. Didn't lose time shifting to 4th.

But with the new 6 spd that's all changed. 3.73's may not be the best in the 1/4 for the 5.0.

Though they may still be sweet for 2 lane twisties.
They were only good for 102.5 mph passes without being in the limiter. In a 300 bhp / 3.55 car we were riding the limiter for the last 100' in 3rd on a 13.2 @ 103.8 run. The 320 bhp (Premium Rating) / 3.73 Car would hit it at the exact same speed. Ford exactly offset the gear change with the limiter bump.

3.73 is good for 111.8 mph (Brembo) or roughly 110 mph trap before hitting the limiter if Tirerack is correct about the OEM Ford Tire being Identical to the OEM MB (They have that tire listed as OEM replacement) at 763 rpm. However several places have listed these tires (OEM Ford Brembo) at 769.5 rpm. Motortrend list max speed in 4th at 110 mph in the same test they went 111 mph but that may be for the 6850 rpm soft limiter instead of the hard limiter.

3.55 will be good for 117.5 mph or 115.5 mph Trap.

Mike from Powerhouse took a "Stock Order" GT Premium with Standard 3.31 and 18" All-Season tires 12.77 at Atco. Unfotunately I have not been able to find out the 60' or MPH. So far I havnt seen anyone beat him with a 3.73/Brembo (Summer Rubber) Car.
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Last edited by Gene K; 5/16/10 at 1:27 PM.
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Old 5/16/10, 1:43 PM   #10
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3.73 is good for 111.8 mph (Brembo) or roughly 110 mph trap before hitting the limiter if Tirerack is correct about the OEM Ford Tire being Identical to the OEM MB
Yeah I hit 105 in 3rd right at the 6500 limiter (without hitting it) with the stock BFG KDWS 235/50x18.
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Old 5/16/10, 2:11 PM   #11
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Originally Posted by BLKCLOUD View Post
Though I'd still like to try 3.73s, its hard to disagree with the above.

Question for you Gene. How is the MT82? I know you just got your car, but does it feel like it can be aggressively shifted? Can you tell if the 4/5 gear can be shifted like the 2/3?

Would you mind pulling the tranny out and taking it apart to see if 5th is on the main shaft?

And congrats on getting your car - very jealous!
Only problems Ive had with shifter is I keep putting it in 6th when I want to back up (Its where reverse was on TR3650) and I keep going from 5th to 4th when looking for 6th. Im not used to having to load the shifter right when pulling back and Im letting the spring push it over. Have to retrain the old muscle memory.

4-5 feels fine but I havnt really pushed it hard enough on a public road to be doing 115 mph power shifts. If it ever stops raining here I will try to get to a 1/4 mile track and find out. Unfortunately thats about all we are likely to find out as its likely to be 90F and 90%.

Shifter is farther back than a 2005-2009 (Dont remember exactly how it compares to a 2010). Shifter has a very nice feel. Does not move with the engine and so far I have yet to miss a gear (Even if I do sometimes hit 4th instead of 6th). You can feel each tooth as it slides in yet its silky smooth and not notchy at all. May be a bit long of throw for the open track boys but strip guys will appreciate the leverage. If and when I miss a shift I will let you know.

I think you can find breakdowns of the trans on Oz Sites as its been used in the Landrover Defender for a while now.

Please do not take the following as "an issue" yet as this is only a sample of one.
Now the one complaint: I have not read this complaint anywhere else so it may be an isolated instance. On some high rpm 1-2 shifts it suffers from LS1 Disease. IE The clutch sticks to the floor. Hopefully it will either go away with more miles (Not likely) or go away with bleeding. If not I suspect a bad slave cylinder.
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Old 5/16/10, 3:15 PM   #12
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Interesting...appreciate the info.
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Old 5/25/10, 9:07 AM   #13
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I was hoping to hear from those who have their cars what their experience with the different gear ratios has been as a DD. I'm not going to be taking mine to the track much but I do plan on punching it when I can and she will be my only car for a couple years at least. I live right on the DC beltway and traffic is a ***** all the time. I went with the 3.73's and a Manual transmission because I value fun and a challenge over ease of use. (I didn't know how to drive stick when I ordered the car).

My main questions are: am I going to hate driving after a week of being in traffic with the 3.73's and a manual tranny? or is it not all that bad and worth it for the thrill. Will I be wanting to swap gears because I plan on taking highway trips? Will 5 hours on route 81 at 75mph feel like the car is working too hard with the 3.73 ratio?

P.S. I don't care so much about hitting the fastest quarter mile possible, but I do want to be punched back into my seat like I was leaving orbit.

Last edited by HokieCodeMonkey; 5/25/10 at 9:11 AM.
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Old 5/25/10, 10:26 AM   #14
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Originally Posted by HokieCodeMonkey View Post
My main questions are: am I going to hate driving after a week of being in traffic with the 3.73's and a manual tranny? or is it not all that bad and worth it for the thrill. Will I be wanting to swap gears because I plan on taking highway trips? Will 5 hours on route 81 at 75mph feel like the car is working too hard with the 3.73 ratio?
I think you're going to love the 3.73 and manual shifter for a lot longer than a week. On the highway, you'll only find the engine spinning ~200 RPM faster @ 70 MPH, so I don't think you'll really notice it. The car will not feel as though it's working harder; it'll actually be more responsive to throttle.
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Old 5/25/10, 11:17 AM   #15
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Originally Posted by HokieCodeMonkey View Post
I was hoping to hear from those who have their cars what their experience with the different gear ratios has been as a DD. I'm not going to be taking mine to the track much but I do plan on punching it when I can and she will be my only car for a couple years at least. I live right on the DC beltway and traffic is a ***** all the time. I went with the 3.73's and a Manual transmission because I value fun and a challenge over ease of use. (I didn't know how to drive stick when I ordered the car).

My main questions are: am I going to hate driving after a week of being in traffic with the 3.73's and a manual tranny? or is it not all that bad and worth it for the thrill. Will I be wanting to swap gears because I plan on taking highway trips? Will 5 hours on route 81 at 75mph feel like the car is working too hard with the 3.73 ratio?.
I bought the 3.73 specifically because of traffic. Atlanta has some of the worst traffic in the US. D.C. is up there, too. The 3.73 gears mean the car will be moving a couple mph slower when in first gear at idle speed. That will make it easier to creep in traffic. My guess / hope is that I'll be able to get the car into first without even touching the gas.

On the highway in 6th, you won't even notice the 3.73s. It's a 200 rpm difference.
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Old 5/25/10, 11:22 AM   #16
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Thanks I thought there was a more significant difference in RPM over 60mph. Also, thanks for the advice on first gear being a slower idle and potentially ideal for traffic in 3.73.

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Old 5/25/10, 11:54 AM   #17
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I have attached a spreadsheet that has rpms for all of the gears / ratios.
Attached Files
File Type: xls rpms.xls (23.5 KB, 362 views)
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Old 5/25/10, 12:06 PM   #18
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Originally Posted by HokieCodeMonkey View Post
. . . I don't care so much about hitting the fastest quarter mile possible, but I do want to be punched back into my seat like I was leaving orbit.
I guess it's all relative to what you are used to -- but I think you are going to get that feeling regardless of which gear set is in the rear end. I know I get it with my 2010 GT and 3.31 gears, and the 5.0 can only be better.

Disclaimer: It's been a long time since I've had a performance car, so my perception of being launched might be a little different from yours!
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Old 5/25/10, 12:32 PM   #19
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I have also read debate over the MPG associated with the various gears.
So, it will be less with the 3.73 but I read that it will hardly matter.
Does everyone else feel that way, or does that put a 3.73 as a daily driver out of the question?

Just my quick thoughts, I figure a loss of about 1-2 mpg from what I read.
So, to make sense of it, about 16-32 miles less on one tank of gas.
So, the extra cost for driving with the 3.73 ratio would be about the cost of 1-2 gallons of gas per fill up depending on realized gas mileage.

Is my thinking about right?

Thanks...
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Old 5/25/10, 12:35 PM   #20
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From reading Gene and coffee's other posts on this, it truly does seem as though 3.31's are similar to running 3.55's in previous set ups. This may be the reason that people who have ordered the "slow" 3.31 gears and haven't noticed much of a performance downgrade of sorts.

Looking at coffee's chart, I am pushing for the 3.55's, they are very similar to the 3.73 with a little more hwy mpg acheivement.

I do love that the 3.31 will run 70 mph at about 1850 in 6th, that's LOW.

I personally want performance and fuel mileage so I think I can live with either the 3.55 or 3.31. The 3.73 may seem useless but I hope the 3.55 has a good creep feel so when I hit Dallas traffic comming home I can easily creep through the interchanges and in downtown.
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