What gears for a 08 GT

[08_stanger]

Hi All,

I'm new to the mustang world and new to these forums. I just bought a 2008 Mustang GT, Deep Candy Apple Red and I'm starting to do some mods to it. I already installed a JLT Cold Air Intake with tuner SCT X3, from Evolution Performance in Aston, Pa and I can feel the difference already. The next mod I want to do is change the gears from 3.55 to 4.10 or 3.90 or 3.73. Has anyone changed their gears and how does it feel on the road. I'm afraid that 4.10 is too much gear for the everyday driver and the highway. If I go with 3.73 thats not much of a difference from 3.55, so it may look like 3.90 gears. Please help me out so I can make the correct decision.

Thanks
Mike

 

[steedman07]

Well, I have an auto and im supercharged, and i drive alot of highway...I have 4:10's, if i had a stick i would have gone with 3:73's..With my centrify, i love how the gear gets me back to boost quick..75-mph, and im at 2500-2600 rpms's..not bad at all..

 

[08_stanger]

I forgot to mention that I have manual.

 

[psfracer]

Are you going with aftermarket wheels/tires in the future? And if you are, any idea how tall of a tire you are going to go with in the rear?

I run 4.10's with a 28 tall tire and its perfect. I have 71K miles on the car, daily driver, no problem at all.

 

[bigcat]

go with the 4.10s, you wont be disappointed.

 

[08_stanger]

How hard is it to change out the gears, I've seen 4.10 ring and pinion gears for about $200.

 

[fobra559]

go with the 4.10s, you wont be disappointed.

^:Word: 4.10's for manuals and your right, going from 3.55's to 3.73's is not that big of a difference.

 

[anthony05gt]

N/A ...4.10's turbo or centrifugal blower 4.10's. Twin screw blower 3.73's.

 

[psfracer]

N/A ...4.10's turbo or centrifugal blower 4.10's. Twin screw blower 3.73's.

Don't forget---it also depends on how tall of a tire you are going to run. I would agree with the above statement with a 26 tall, but not a 28 tall.

 

[08_stanger]

I still have the factory tires and wheels installed. They are 235/50R 18inch. How much of a difference would that matter.

 

[anticubicle]

4.10's

 

[psfracer]

Well, put it this way. My 4.10's with a 28 tall tire is like a 3.90 gear with a 26.5 tall tire.

Here is a calculator that will help you see the difference. You will need to know the diameter of the tire, then divide by 2 to get the RADIUS.

You will also need to know the overdrive ratio in the transmission. For racing you always use a 1:1 ratio for the trans, but in your case I would think you would want to see the rpm when you drive on the freeway at different speeds, and you would be in overdrive which is the following:

.675 for the 5 speed manual GT
.710 for the 5 speed auto for V6 or GT
.720 for the 5 speed manual V6

Plug in the numbers here to see what you get.
http://wahiduddin.net/calc/calc_speed_rpm.htm

 

[MikeysOTP]

No doubt about it, 3.73s are not enough with the 18s. I had mine installed before I took delivery of my car after test driving one with the 17s and 3.55s. Using that as a guideline I ordered my car with 3.31s and had the dealer do the swap when it came in. I have regretted it ever since, these cars love more gear. I even know a guy running 10.5 psi on a Saleen twin screw with a manual and he insists the 4.10s are still not too much.

I am not sure why some people say 3.73s with manual and 4.10s with auto since Ford says the exact opposite. Look at the FR2 Drag Pack offered by Ford and you will see what I am talking about. The manual must have a different ratio even though both the auto and manual are 5 speeds.

Finally, do not skimp on parts to save a couple of bucks. Get the good gears from Ford or you might end up with the dreaded gear whine many others have ended up with. Having to buy new gears and paying for a re-install would really suck.

 

[DarkFireGT]

When I see advice on gears, I've generally noticed that people who have forced induction and recommend 3.73's have better track times than people who recommend 4.10's and have forced induction. My take on it is if you plan on going FI, go with 3.73's. If you have no plans of FI, then 4.10's.

 

[anthony05gt]

Don't forget---it also depends on how tall of a tire you are going to run. I would agree with the above statement with a 26 tall, but not a 28 tall.

Boost level, tire type, tire brand, average ground temperature, and driver's intentions are also factors. We could go on and on about this until we're all blue in the face. My '05 has been n/a, n/a with all the typical bolt ons, F/I with Procharger, (different boost levels) and F/I with Whipple. With all that in mind, if I were to drive this car with a set of 17'' Mickeys on the street rather than my Michelins, I might suggest something different. It's all subjective.

 

[PUNISHER RACING]

My car has 3.73's my brothers has 4.10's both feel about the same through the midrange, with the 4.10's def. having better low end grunt. However there is a def. difference on the highway with the 3.73's they don't have that held back feel in 5th like the 4.10's do. If I did it over I would use the 3.90 gearsets in the everyday driver. Both still manage 25 mpg on highway trips though!

 

[psfracer]

When I see advice on gears, I've generally noticed that people who have forced induction and recommend 3.73's have better track times than people who recommend 4.10's and have forced induction. My take on it is if you plan on going FI, go with 3.73's. If you have no plans of FI, then 4.10's.

I have seen the exact opposite. I run 4.10's and I 60' 1.49. I have a friend with a whipple at 18psi, with 3.73's and can only 60' in the high 1.5's. I think the problem is if your going 4.10s with alot of boost, you better have the tire and suspension to put the power to the ground. If you don't, then yes, the 4.10's will do more harm then good.

With a 28 tall tire, at 6500 rpm, with 4.10's you can go 132mph in the 1/4 mile.

That being said, the thread starter is N/A, daily driver, manual trans. So as long as he doesn't end up going with a short tire, I stand by my thought the 4.10 would be best, especially since he already has 3.55's, and a jump from 3.55's to 3.73 wouldn't be worth the expense in my mind. I posted the gear calculator in post #12 so he could decide.

 

[DarkFireGT]

I have seen the exact opposite. I run 4.10's and I 60' 1.49. I have a friend with a whipple at 18psi, with 3.73's and can only 60' in the high 1.5's. I think the problem is if your going 4.10s with alot of boost, you better have the tire and suspension to put the power to the ground. If you don't, then yes, the 4.10's will do more harm then good.

With a 28 tall tire, at 6500 rpm, with 4.10's you can go 132mph in the 1/4 mile.

That being said, the thread starter is N/A, daily driver, manual trans. So as long as he doesn't end up going with a short tire, I stand by my thought the 4.10 would be best, especially since he already has 3.55's, and a jump from 3.55's to 3.73 wouldn't be worth the expense in my mind. I posted the gear calculator in post #12 so he could decide.

I guess I was talking about amateurs. You seem to have a bit of experience. But I've seen plenty of amateurs both on here, and at the track, strap on a blower and still stay in the 12's, because they don't have the experience needed. But, I digress. You have more experience than I, so I will agree with your opinion.

 

[psfracer]

Actually I think we are saying the same thing then.

---Because I totally agree, 4.10s without the proper setup will hurt you, not help. To take your example, if you threw on a whipple at 10psi, put on 4.10s, then showed up at the track with street tires and a stock suspension, you would be disappointed for sure.

 

[08_stanger]

I wouldn't say I was a amateur at racing, I do have about 8 years of racing. But that has mostly been with my 67 chevelle. This whole mustang world is new to me. My dad works for Ford and when it came time to buy a new car he insisted on to me to take a test drive with the 08 mustang. I must say and admit that being a classic chevy lover for over 30 years and having my chevelle for the last four years, that I am so impressed what Ford did with the mustang. It was really embarresing driving up to work the first day with my new mustang and all my friends know how big of a chevy fan I am. Yeah they gave me crap for a couple of weeks, but once they got into the car and I took them for a test drive, they understand now.

As far as the gears go, it looks like I'm going with the 4.10's. There is still other mods I want to do with the car in the next couple of months.

If anyone is wanting to put a Cold Air Intake on, go with the JLT and SCT X3 Tuner. I just installed mine and what a huge difference.

Thanks for all your help gentlemen and as soon as I can shrink my pictures down of the cars I will post them on my gallery.

Go Air Force!!!!

Mike