3.73 gears VS. 4.10

AguynamedJay · 11-13-2006, 08:09 PM

I have an 06 GT with the 5-speed. I was considering the 4.10 gears but my mechanic ( a racer dude whom I trust) suggested the 3.73's instead. He said the 4/10's are quicker but the high revs and the whine are enough to drive you bonkers on any long trip and the gas mileage dies. H esaid he had 4/10s but swapped them out becasue of the noise...

So does anybody have the 3.73's and is it worth the cost to move up from the 3.55s?

A humble new guy,

Jay in the OC

jmart69x · 11-13-2006, 08:46 PM

I've got an 06 GT 5-speed with 3.55 gears. I too am considering upgrading my gears, and I was thinking of 3.90's. Several experts have told me to go with the 4.10's because of the better bang for the buck. In terms of the gas mileage issue, I have heard and read several posts on the forum that the decrease is insignificant (1-2 MPG decrease on hwy). Thanks for the heads up though about the whining issue. I am going to look into that before I make the plunge.

Maveric · 11-13-2006, 10:29 PM

I am a humble new guy also,

Yet I have 4.10's in the rear and I really don't notice anything "anoying" about them. Yet it did take a quick tune.

Maveric

mustangman02232 · 11-13-2006, 11:26 PM

you have a 5 speed? thats easy go with 4.30s, no im not kidding, with the t3650, it has a 5th gear of .62 and a 27" tall tire you will be around 3k at 80 mph, my budddy has 4.10s in his 99 (t45 4.10 = 4.30 in t3650) and was still getting 21 mpg at 70ish mph

smt636 · 11-14-2006, 06:59 PM

i've got 4.10s in my truck and they don't whine...i'm guessing if his gears where whining he didn't have his backlash set correctly. but if you dont do many long road trips i wouldn't worry with the swap...do it and enjoy. but if you take many road trips the high revs at cruising speed does get annoying...or at least it does to me. wouldn't be that bad if i had another gear, but i dont. i'm about 2700 rpm at 80.

i don't think you'd notice a big enough difference between 3.55 and 3.73 to warrant the swap. 3.55 to 3.90 would be the minimal i'd do.

06hoss · 11-14-2006, 08:04 PM

Hey guys, I still have the 3.55 rear end and I am probably going to only go to 3.73. I've read of a ton of stuff about which gear ratio to go with and I'm only going with 3.73 because I want to leave the possibility to add a supercharger later. From what I've read when you go with a SC, you add so much torque that the extra gearing isn't needed. In fact, KB says no extra gearing is needed on their website. BUT, if you are going to stay normally aspirated, then from everything that I've read, a 4.10 rear is the way to go. A 3.90 is a nice compromise between the two ratios, but I think that Ford Racing doesn't sell that ratio and the consensus seems to be that Ford makes the best gears.
smt636 is right about the gear whine...that happens when the backlash isn't set correctly. There are shims that have to be installed in order to get the backlash right and sometimes it takes more than one try and some installers will get lazy and not do it a second time to get the backlash right. They also have to get the pinion depth correct, but it's usually incorrect backlash that will make the gears noisy.

[IMG]local://upfiles/48298/986332C0B82E42BB95EABF545D82016D.jpg[/IMG]

mustangman02232 · 11-14-2006, 10:13 PM

Quote:

ORIGINAL: 06hoss

Hey guys, I still have the 3.55 rear end and I am probably going to only go to 3.73. I've read of a ton of stuff about which gear ratio to go with and I'm only going with 3.73 because I want to leave the possibility to add a supercharger later. From what I've read when you go with a SC, you add so much torque that the extra gearing isn't needed. In fact, KB says no extra gearing is needed on their website. BUT, if you are going to stay normally aspirated, then from everything that I've read, a 4.10 rear is the way to go. A 3.90 is a nice compromise between the two ratios, but I think that Ford Racing doesn't sell that ratio and the consensus seems to be that Ford makes the best gears.
smt636 is right about the gear whine...that happens when the backlash isn't set correctly. There are shims that have to be installed in order to get the backlash right and sometimes it takes more than one try and some installers will get lazy and not do it a second time to get the backlash right. They also have to get the pinion depth correct, but it's usually incorrect backlash that will make the gears noisy.

[IMG]local://upfiles/48298/986332C0B82E42BB95EABF545D82016D.jpg[/IMG]

do you plan on a centri or twin screw? a centri with 4.10s will be fine, for NA and 5 speeds 4.30s are actually good gears,

ChristianaMuscleCar · 11-14-2006, 10:18 PM

The gears should not whine...there must have been a problem with his gear set. I would go with the 4.10's. If you are going to make a swap do something that is going to make a real difference.

Good Luck!

06hoss · 11-14-2006, 10:49 PM

Twin screw Mustangman...most likely a KB. I want the down low punch of a twin screw, plus my car will be strictly street so I won't need all that top end that the centrifugal will provide. I was just reading about another guy on this forum who just put the KB blower on himself and he already had 4.10s and now he's got it back in the shop taking it back down to 3.73. He said he could spin the wheels going 55 with an auto trans...way too much torque. Some guys run the 3.55s with their twin screws. You're right though, the 4.10s might work with a centri since they need help down low.

AguynamedJay · 11-15-2006, 02:23 AM

Hey All me again...

My mechanic whom I trust suggested going with 3.90 gears instead of the 4.10's...
He is a mopar guy all the way but knows his cars and has raced (successfully). He said I would still get lots of oomph! without the issues related to the 4.10's. I see that CJ Pony Parts lists them yet I can't find them in my Ford Racing parts book...?
Once again I am looking for suggestions and experience with them if anybody has it.

Thanks Gang!

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