4.09 gears?

07 Black Beauty

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I'm leaning towards swapping to 4.09 gears on my 350 R, and wanted to get some feedback. Is there a noticeable difference? On my 14gt500 going from 3.31 to 3.73 made the car much easier and more enjoyable to drive especially around town.
 

me32

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. And yes with the gt350 R the 409 should make the car feel peppier since the power band is all upper RPM
 
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biminiLX

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Still surprised more haven't done this.
I've made a decision to get either a GT350 or Backdraft Racing Cobra roadster this spring and any GT350 will get 4.09s immediately.
If it's anything like my Charger, you can buy a complete center diff with gears and basically bolt into IRS with only 2-4 shop hours tops.
Why haven't more of you guys gone 4.09s?!
As above, this car if keeping NA is begging for gears.
-J
 

GT Premi

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Probably because people were saying they don't make gears for the GT350. That never did make any sense to me.

To the people who have done it, is the 4.09 noisier than stock? Also, what brand and where did you purchase?
 

07 Black Beauty

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Probably because people were saying they don't make gears for the GT350. That never did make any sense to me.

To the people who have done it, is the 4.09 noisier than stock? Also, what brand and where did you purchase?


Ford Racing makes the 4.09, if you go 4.56 Yukon makes them. I've always been told to go with Ford Racing gears which is what I plan to do on the 350 for my first mod.
 

ANGREY

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I'd love to swap to 4.09's, but I'm terrified of secondary issues (new noises, whines, clunks, etc). Hell, there's even a placebo effect I'm sure where I end up listening closely after a rear end swap and probably hearing things that were always there before but I just didn't focus on previous.

Perfection would be a steeper rear and a corresponding swap out of 6th to maintain cruising RPM. Most everyone can agree that 6th is useless for anything other than a highway cruising gear, so having livelier 1-5 and a "normal" 6th would be ideal.
 

GT Premi

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A 4.09 would definitely fix that, but I still wouldn't use 6th for trying to accelerate.
 

07 Black Beauty

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I'd love to swap to 4.09's, but I'm terrified of secondary issues (new noises, whines, clunks, etc). Hell, there's even a placebo effect I'm sure where I end up listening closely after a rear end swap and probably hearing things that were always there before but I just didn't focus on previous.

Perfection would be a steeper rear and a corresponding swap out of 6th to maintain cruising RPM. Most everyone can agree that 6th is useless for anything other than a highway cruising gear, so having livelier 1-5 and a "normal" 6th would be ideal.

Yeah a noisy rear is definitely a concern. When I swapped to 3.73's on my 14 gt500 it was factory quiet, but I know that's definitely not always the case. I wish I could find a rear with the 4.09's factory installed rather than opening up the rear on mine and hoping for the best
 

ANGREY

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Took the plunge and ordered the FRPP 4.09s for the Super 8.8. (M-4209-88409A).

US Gear makes the same ratio as well as others and offers "stealth" and I'm not sure if the FRPP is 2 angle or 5 angle, but I figured I'd better go with Ford parts if I want a shot at not having additional noise.

$236 shipped. Once it comes in I'll find a reputable shop to swap them.

Given that I have only 17k miles, I wouldn't think I need new bearings and I'll ask the shop if they need me to supply the installation kit. Is it foregone conclusion that I need new bolts for the locker?
 

Ablaze

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Good luck ANGREY! I kept hearing of the GTs outrunning the GT350 and always shook my head at the thought. I look forward to hearing your results.
 

662

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I'm very interested in the outcome and if it makes the car better on the track... My buddy drives a modified Viper and he walks from me (albeit slowly) on the straights... I am thinking E85, but sourcing the fuel seems difficult, if the gears can help pull harder it may be worth the budget. Don't need much - famous last words

Do you know the rpm vs. speed ranges for the 6 transmission gears 4.09 vs. stock and what's stock gear?
 
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tt335ci03cobra

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I’d go with 4.56, it would be very fun on a high rpm, stickshift car like these. If the stock car came with 4.56’s, it wouldn’t seem out of place imo.

Here’s a gear calculator to get an idea
Wallace Racing - Calculate Speed for given RPM, Rear Gear Ratio and Trans Gear Ratio

The gears are

1. 3.25
2. 2.23
3. 1.61
4. 1.24
5. 1.00
6. .63

Tires are 28” tall.

As an example:

•3.73 (stock) 6th@70mph is 2000rpm
•4.09 6th@70mph is 2175rpm
•4.56 6th@70mph is 2425rpm

Another example:

With 4.56

1st@8200 46mph
2nd@8200 67mph
3rd@8200 93mph
4th@8200 120mph
5th@8200 150mph
6th@6000 165mph (probably new top speed because less hp at 165mph than the stock gears which would be 5th at almost redline with 3.73’s)

But short of top speed runs, it’d be very fun
 

ANGREY

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Stock is 3.73 and the only 2 options are FRPP 4.09 and Yukon 4.56s
E85 and 4.09s would be a great improvement IMO, good luck.
-J

US Gear makes a 3.73 a 4.09 and a 4.11 for the super 8.8 IRS. They're coming out with a "stealth" series next year that supposedly is quieter (I'm assuming a 5 angle cut instead of 2 axis like most gears.)
 

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