[Shaun03GT]

Ive been thinking latley to go back to 4.10s. I like the 3.73s for the fact of being able to hit 130mph at the top of 4th, but I barley ever do that. Id get a lot more use out of a lower gear.

Running 3.73s I got my quickest ET, but my trap speed was never as good with the 4.10's. Plus I barley got any practice in with the 4.10s. I trapped 117mph and 116mph with the 4.10s, quickest with the 3.73s on a cool night was 115, but mostly low 114's high 113's.

Ive been thinking though, even 4.30's. I shift at 6300rpm. My tuner told me Id have to problem revving to 6500rpm because my car never really dipped on power. But say 4.30's with stock tires at 6300rpm thats 112mph, and to 6500rpm about 115mph. But, if I ran a 28" tire. Id be able to hit 122mph at 6300rpm and 126mph at 6500rpm.

Im not sure if I want to though, it is nice being able to hit it on the highway and let the car wrap out alittle, but a lower gear I think would benefit a lot. 4.30's with a centri I think would be nasty. You dont really see anyone with that low of a gear and boost. Opinions?

[Shaun03GT]

Also, since I just had my rear end rebuilt this past February, do I need a new bearing set? Or can I just re-use everything?

[jivepepper]

If you plan on making more power then I'd say 3.73's. If you ever get to where you're spinning the motor to 6500 rpm+ then you can but the 410's in and still do 130.

[bulloch27]

I wouldn't touch 4.30s unless you're going with the 28" tire for sure.

[jivepepper]

Originally Posted by bulloch27 I wouldn't touch 4.30s unless you're going with the 28" tire for sure.

and or running higher RPM. I use to run up to 6400 rpm with stock heads but with the SC and cams I was still making power at 6400.

[DickH]

id skip steeper gears + taller tires and just go with whatever gear matches your trap now if that is what you are worried about. Maybe get the 4.10s, and then save up money for whatever so you can extend your RPMs some. I am sure centri blower going out to 6800rpms with 4.10s wouldnt be a bad mix.

[bulloch27]

A 28" tire will cushion your launch like you can't believe but I think the 4.30s probably still too much. I run a 4.10 with 28" and run out in the quarter....... I typically only run the 1/8 though. 6200 RPM w/ 4.10 and 28" tire is 118 MPH. Keep that number in mind.

[Shaun03GT]

4.30s and a 28 tire would be less gear then 4.10s and stock tires. Thats why i was thinking that. I'm definitley going to atleast 4.10s I miss them .

[stal94gt]

i stepped up the gearing min my cobra to 3.73's and it made little diff. i trap about 1-2 mph higher with the 3.73's but it is almost a perfect matched gear for my car and power. 4.10's in your car would probably be a better fit gear untill you start getting into the 500 hp range. even then a 28 inch tire has huge advantages over a 26 inch. next year im getting rid of the 26 inch slicks for 28's. if i were you and can do the gear swap on your own i would do it. the only thing i would swap out is the pinion bearing, crush collar, and pinion seal. rest of it will be ok.

[eddy21x]

4.30's FTW i dd my car with them
no complaints here

[mcqueen]

For DD use, I loved the hell out of my 4.10s but I wouldn't have gone any higher. My old V6 was maxing out at 18mpg with them, I had to shift before I got through an intersection, and in the snow/ice I couldn't use 1st gear (hell, I spun out at 25mph in 3rd while slipping the clutch).

[Shaun03GT]

Originally Posted by stal94gt i stepped up the gearing min my cobra to 3.73's and it made little diff. i trap about 1-2 mph higher with the 3.73's but it is almost a perfect matched gear for my car and power. 4.10's in your car would probably be a better fit gear untill you start getting into the 500 hp range. even then a 28 inch tire has huge advantages over a 26 inch. next year im getting rid of the 26 inch slicks for 28's. if i were you and can do the gear swap on your own i would do it. the only thing i would swap out is the pinion bearing, crush collar, and pinion seal. rest of it will be ok.

1-2mph? Thats pretty good. Just from 3.55 to 3.73s. I do miss the 4.10s they were fun. Idk, Im still thinking about 4.30s but Im sure it will be a lot. But like I said, I think those matched with a 28" tire will be fine for the stock motor. Until I build the motor and can rev to 7000 with a 28" tire, that would give me about 135mph. So Idk, I mean I could always go back to 4.10s or 3.73s. What do you think? BTW Ill probably be doing the install myself, gears are the only thing I havent done, but I feel comfortable with myself to do them.

Originally Posted by eddy21x 4.30's FTW i dd my car with them no complaints here

Yeah, dont you have spray on your car too?

PS this will be my 3rd gear swap.. Went from stock to 4.10s, then to 3.73s, and now either 4.10 or 4.30's

[Shaun03GT]

Just for an idea, this GT runs 4.10s with 28" tire and makes alittle over 500rwhp and seems to hook fine.

Built Vortech 02 GT vs APS TT G35, 71mm Supra & HCI 03 Z06 - YouTube

Built Vortech 02 GT vs APS TT G35, 71mm Supra & HCI 03 Z06 - YouTube

[Shaun03GT]

Found this too, Mach 1 with 4.30s and a Procharger

2004 Mustang Mach 1 - ProCharger 30-120 Speedometer - YouTube

2004 Mustang Mach 1 - ProCharger 30-120 Speedometer - YouTube

[stal94gt]

I think you should do it as long as you do the install. Its an easy job just ask questions before you start

[Eagle2000GT]

You've been wanting to go back to 4.10s for some time. I've also noticed that you're willing to push the motor a lot further into the red than I am.

On the track, ideally you'd be hitting maximum rpms as you pass the finish line. My calculations of the rpm/speed that your considering come out to be a little slower than yours. For example, I get 117-118 mph for 4.30s with a 28" tire at 6300 rpms and 113-114 for 4.10s with a 26" tire at 6300 rpms. But its probably a rounding error. I'm using using the loaded stock size tire which has a diameter of approximately 24.9" and a loaded 28" tire diameter of 27.2".

I think 4.30s will be too much gear if you run 26" tires. You will have to run a 28" tire. And then it would be close. Mounder27 reported running 4.30s with a 28" tire. He's reported a nice 1.5 60 ft. But I think he's only running 1/8th tracks. He didn't report a 1/4 mile time.

With 4.10s and a 26" tire you will be pushing it to 6500 rpms. If you pick up some trap speed you'll be pushing it even higher. I'm not sure why you're focused on trap speed instead of ET but if your going to do this then 4.10s with a 28" tire on 15" wheels seem to be a good combination. That should be around 123-124 at 6300 rpms and it should get you into the 11s. From some of the posts that I'm been tracking it also give you a shot at a 1.6-1.7 60 ft. SaxmanJJ reported a 1.54 60 ft.

Switching back to stock size tire for the street shouldn't be too bad either assuming your easy on the throttle. I believe you have a T3650 transmission with a .62:1 fifth. I have a T45 with a .67:1 fifth and 3.73 gears. In fifth at 75 mph my car is running around 2530 rpms. Your car with 4.10s would be around 2570. Not much different. You might top out in fourth early but on the street you still have fifth gear.

[Shaun03GT]

Thanks for the info Tom. I have trapped 117 with the 4.10's and i was going through right as my shiftlight went off at 6300rpm. 4.30s might be alittle much, ill have to think about it

[Shaun03GT]

Also I like trap speed for some reason, and my car felt faster with the 4.10s. Car feels alittle lazy in 4th compared to the 4.10s

[Eagle2000GT]

Originally Posted by Shaun03GT Thanks for the info Tom. I have trapped 117 with the 4.10's and i was going through right as my shiftlight went off at 6300rpm. 4.30s might be alittle much, ill have to think about it

You should be OK then. I don't have a shift light so I have to estimate my rpms from lower speeds. In fourth at 80 mph I'm running approximately 4000 rpms (actually its 3950). When I did the calculations using 3950 instead of rounding to 4000 it came out much closer to your shift light.

Calculations for 4.10s at 117 mph: 3950/80x117 = 5777x1.0992 = 6350 rpms
Calculations for 4.30s at 117 mph: 5777x1.153 = 6661 rpms.

[eddy21x]

yeah dude 4.30's stock converter and 90 shot
dont fear the gear

i do highway quite often too
mpg aint changed to much
pulls alot harder and i trap around 104 n,a
with more rpm to go