2013 GT500 3.73 gears - Mustang Evolution

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Old 06-01-2013, 01:19 AM   #1
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2013 GT500 3.73 gears

I would appreciate comments from anyone who has a 2013 GT500 with 3.73 differential ratio. Mine is at Shelby American being turned into a wide body (front and rear) Super Snake with the 850 hp Kenne Bell blower. It's due to be completed in the next two to three weeks. The stock 662 hp will shred the tires with the stock high gears. The wide body kit adds over six inches of rubber on the rear (but its making nearly 200 hp more). The high gear ratio made the car very "drivable". I'm kind of on the fence about changing to the lower 3.73 ratio (mechanical advantage of low ratio versus drivability of high ratio). So ... Any thoughts from those who have made the swap? Thanks!
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Old 06-01-2013, 01:37 AM   #2
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Lol not sure if many people on here are lucky enough to own one of those. I'dask at svtperformance
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Old 06-01-2013, 01:02 PM   #3
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I think that 3.73s will help you clutch but hurt your tires but at 850 crank hp your going have trouble with tires anyway...get some drag radials and don't drive in the rain and you'll be golden...good luck and don't forget to post pics when it's all finished
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Old 06-01-2013, 01:39 PM   #4
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Changing the gear ratio isn't going to stop the tire shredding @ 850 crank hp.
You'll just have to get used to it..
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Old 06-01-2013, 01:45 PM   #5
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To much power for those tires. Its a bitter sweet thing
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Old 06-01-2013, 04:36 PM   #6
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I have a 13 with 3.73's and 700 lbs of torque at the wheels...it shreds the goodyears easy. I've had a few good launches on some 295/55/15 et streets at 15lbs, but still can only manage a 1.70 60ft. If you drive the car nice it's actually nice on the street, just be cautious when getting on it hard.
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Old 06-01-2013, 05:22 PM   #7
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I have a 13 with 3.73's and 700 lbs of torque at the wheels...it shreds the goodyears easy. I've had a few good launches on some 295/55/15 et streets at 15lbs, but still can only manage a 1.70 60ft. If you drive the car nice it's actually nice on the street, just be cautious when getting on it hard.
It will have Michelin Pilot Sport 345/zr30/20's on the back. I'm not really concerned about shredding tires because that will happen no matter what I do. I just want it to still be a nice driver. Is there anything about the 3.73's that you don't like as compared to the stock gears? Thanks!
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Old 06-01-2013, 05:47 PM   #8
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Well, I did lose a bit of gas mileage and top end speed with the gear swap, but that is to be expected. As for being a nice driver, I think it's more fun now, gets the rpm's up a bit more instead of lugging around low all the time.
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Old 06-03-2013, 01:25 PM   #9
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Thank You

Thank you all for your informed responses. I called Shelby American this morning and ordered the 3.73 gear change.

Chip
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Old 06-03-2013, 02:00 PM   #10
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Cool, I'm sure you'll like it!
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Old 06-04-2013, 10:07 PM   #11
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Someone correct me if I'm wrong. I'm almost 100% sure that I'm right but still... It does not matter much how wide your tires are but how much your wheel weighs. Since wider tires normally equal wider wheels, people seem to think that wider tires give them more grip. But the formula for friction is force of friction = mu* normal force. Mu is a constant so that never changes and normal force is only changed by the mass of your car. Therefore. Heavier wheels = higher normal force = more friction. Width does not come into play there at all. Hope this helps you with any tire dilemma
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Old 06-05-2013, 01:29 AM   #12
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Someone correct me if I'm wrong. I'm almost 100% sure that I'm right but still... It does not matter much how wide your tires are but how much your wheel weighs. Since wider tires normally equal wider wheels, people seem to think that wider tires give them more grip. But the formula for friction is force of friction = mu* normal force. Mu is a constant so that never changes and normal force is only changed by the mass of your car. Therefore. Heavier wheels = higher normal force = more friction. Width does not come into play there at all. Hope this helps you with any tire dilemma
The weight of the wheel is insignificant when compared to the mass of the vehicle. The only thing between the ground (immovable object) and the vehicle (object at rest that wants to stay that way) is the torque applied through the tire contact patch. The bigger the better.
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Old 06-05-2013, 07:58 AM   #13
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Someone correct me if I'm wrong. I'm almost 100% sure that I'm right but still... It does not matter much how wide your tires are but how much your wheel weighs. Since wider tires normally equal wider wheels, people seem to think that wider tires give them more grip. But the formula for friction is force of friction = mu* normal force. Mu is a constant so that never changes and normal force is only changed by the mass of your car. Therefore. Heavier wheels = higher normal force = more friction. Width does not come into play there at all. Hope this helps you with any tire dilemma
My bicycle wheel is pretty light and it's hard as hell to spin...
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Old 06-05-2013, 10:36 AM   #14
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The weight of the wheel is insignificant when compared to the mass of the vehicle. The only thing between the ground (immovable object) and the vehicle (object at rest that wants to stay that way) is the torque applied through the tire contact patch. The bigger the better.
That is an excellent point! You have a good path I'm just wondering how it works according to physics because like I said. That physics equation has no effect from width. But maybe I'm missing something cause your point seems really good

---------- Post added at 11:34 AM ---------- Previous post was at 11:33 AM ----------

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My bicycle wheel is pretty light and it's hard as hell to spin...
Let me know when you can exert 350 ft-lbs of torque on your bike wheels hahaha.

---------- Post added at 11:34 AM ---------- Previous post was at 11:34 AM ----------

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My bicycle wheel is pretty light and it's hard as hell to spin...
Unless you're talking about motorcycle.... I assumed you were talking about a pedal bike....

---------- Post added at 11:36 AM ---------- Previous post was at 11:34 AM ----------

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My bicycle wheel is pretty light and it's hard as hell to spin...
Think about it this way. When we travel 20 mph on our pedal bikes and then slam on the brakes we leave a long long skid mark (no traction). If we travel 20 mph in our car and slam on the brakes, we almost come to an immediate stop
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Old 06-05-2013, 12:23 PM   #15
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but here's the deal if you have the exact same wheels one with narrow tires on then and some with wide tires on which one has more traction??
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Old 06-05-2013, 01:58 PM   #16
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but here's the deal if you have the exact same wheels one with narrow tires on then and some with wide tires on which one has more traction??
I know. I believe the wide ones have more traction too but I've never tested it. My friend put 305 on his car that usually had 235 but got a lighter wheel to balance out the weight an he didn't see much difference in launching :/ but you're right! I'm just looking for someone to tell me the physics behind why I'm wrong...cause ultimately I think I am
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Old 06-06-2013, 09:53 AM   #17
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Lol somebody has some beastly legs if they can burnout on a pedal bike hahaha!

There are so many variables that come into play here it's going to be difficult to have a cut and dry explanation. Also, I don't think that any two scenarios will be the same, everyone's car is tuned and modded differently as well as operate in different climates which can all affect tire grip. Also. A tire from one company will hook better than the same size tire from a different company. Now if we could make all the dynamic variables in this situation a constant, everything from mechanics of engine through the drivetrain as well as driving style and throttle input, I am inclined to agree with the idea that the wider tire with more contact patch will provide more traction for the straight line drag. When you have a car as powerful as ours you start to realize how important good tires really are. They are the only conduit between all that grunt and the road.

Now having said that, I have heard that ford svt chose the 285 width tire for the rear because they felt that any wider than that would cause under steer to show it's ugly head, and that was something they were trying to get rid of with the shelby. Personally I haven't upgraded my tires yet, I'm waiting for the stock good years to go bald. I will get a new set of wheels and I'm leaving towards nitto for the rubber. I have heard positive feedback about their NT05 and the invos.
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Old 06-06-2013, 10:24 AM   #18
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My point on the bicycle comment was to show that it's simply just not the worthy or the width of the tires or wheels, like its been said, many factors, lol.
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Old 07-13-2013, 09:21 AM   #19
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2013 Super Sanke gears

I live in Las Vegas and own a 2013 Super Snake with the KB 850 HP setup (#38, delivered 4/2013). I changed the gears to 3.73 a couple of weeks ago and it was well worth it. The stock gears are simply not practicle. It is hard to drive it with them in slow stop and go traffic and you have to do over 70 to use 6th gear. On a 2 1/2 mile track I might as well have had a powerglide since I could rarely even get into third. I drove it to Shelby to get it tuned after the gear change to make the speedo and supercharger work properly and you will be hard pressed to find anyone else qualified to do that for you correctly if you delay the change. My advice is that you have Shelby do it in the first place. BTW, they told me that mine is the ONLY 2013 SS with these gears anywhere that they know about, except for the prototype car they made. Congratulations and I hope you love your car as much as I do mine.
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Old 07-13-2013, 01:14 PM   #20
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I live in Las Vegas and own a 2013 Super Snake with the KB 850 HP setup (#38, delivered 4/2013). I changed the gears to 3.73 a couple of weeks ago and it was well worth it. The stock gears are simply not practicle. It is hard to drive it with them in slow stop and go traffic and you have to do over 70 to use 6th gear. On a 2 1/2 mile track I might as well have had a powerglide since I could rarely even get into third. I drove it to Shelby to get it tuned after the gear change to make the speedo and supercharger work properly and you will be hard pressed to find anyone else qualified to do that for you correctly if you delay the change. My advice is that you have Shelby do it in the first place. BTW, they told me that mine is the ONLY 2013 SS with these gears anywhere that they know about, except for the prototype car they made. Congratulations and I hope you love your car as much as I do mine.
Congratulations on your new ride. Did you dyno it? Results?
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Old 07-13-2013, 11:22 PM   #21
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I live in Las Vegas and own a 2013 Super Snake with the KB 850 HP setup (#38, delivered 4/2013). I changed the gears to 3.73 a couple of weeks ago and it was well worth it. The stock gears are simply not practicle. It is hard to drive it with them in slow stop and go traffic and you have to do over 70 to use 6th gear. On a 2 1/2 mile track I might as well have had a powerglide since I could rarely even get into third. I drove it to Shelby to get it tuned after the gear change to make the speedo and supercharger work properly and you will be hard pressed to find anyone else qualified to do that for you correctly if you delay the change. My advice is that you have Shelby do it in the first place. BTW, they told me that mine is the ONLY 2013 SS with these gears anywhere that they know about, except for the prototype car they made. Congratulations and I hope you love your car as much as I do mine.
How's the traction?
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Old 07-14-2013, 06:22 AM   #22
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Super Snake Traction

I have not dyno'd the car as the only drive train mod I have done so far is the gears and I am pretty confident in Shelby's claims about this combo. Regarding the traction, in some respects everyone who asked about it is correct. if you shut off the traction control function you will have a real problem staying on the pavement. Even when going 50-60 MPH, hitting the gas without it requires countersteering to remain in your own lane. But when you use the traction control it is surprisingly effective. The kind of burn-out smoke all over the place does not happen. But guys who like pushing it without using TC wind up on a first name basis with the Michelin Man.

One more thing about the gears. If you floor it when under 2K rpm these cars bog down and the warning lights all come on until you shut it off and "reboot" it. One more reason for using a higher ratio rear end like the 3.73 (or higher).

One last point regarding handling. People who write about these cars only being good for a straight line are talking about older Mustangs. The suspension on these new ones is unreal and they stay flat on the track like a slot car. I had an 09KR before this car and the technology between the two absolutely cannot be compared. To me anyway, the handling nothing less than unbelievable.
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