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4:10s on an Automatic


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Just wondering if outting 4:10s on an automatic daily driver would pose any issues? A few people I have asked locally seemed to think that 3:73s should be the max for the automatics but not sure why?

 

So is there a real technical issue or reason not to go with the 4:10s?

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You need to ask someone at SAI. John Walker when he was there had recommended to me not to use certain rear ratios for the cars. It has not only to do with your transmission but SCed or not, usage desired..etc... If I could remeber that far back about what whs said I would relay the info to you. But I can't remember . I would IM one of the gurus at shelby to get the strait scoop.

 

Good luck.

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Not sure who the SAI experts are, but if they want to chime in that would be great!

 

:shrug:

 

 

I would suggest you talk with Gary Patterson. He's driven more of these cars in many combinations than anyone else and will be able to get you good info. He doesn't participate on this forum often so either email him or call Shelby American.

 

I was going to change mine and decided to leave them alone based on Bud's advice. Don't remember all the reasons but noise was one.

Edited by twobjshelbys
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I would suggest you talk with Gary Patterson. He's driven more of these cars in many combinations than anyone else and will be able to get you good info. He doesn't participate on this forum often so either email him or call Shelby American.

 

I was going to change mine and decided to leave them alone based on Bud's advice. Don't remember all the reasons but noise was one.

 

 

I'm not an expert but as Tony mentioned noise is a factor when you start going above a 3.90 ratio. When the Shelby GT's were being designed there was going to be two different rear end ratios depending if the car was an manual or automatic. I'm not positive but I want to say the manual trans cars were going to be 3.73 ratio. Anyway it was decided that having two different rear end ratios would complicate the build process so a compromise was to fit all SGT's with 3.55s

 

Personally I wouldn't run 4.10 gears with an automatic due to the noise and the additional transmission heat.

 

Steve

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Personally I wouldn't run 4.10 gears with an automatic due to the noise and the additional transmission heat.

 

Steve

 

 

Thats interesting Steve, I would had never considered transmission heat as an issue...figured with high quality lube, it would be fine.

 

Thanks for the input!

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I put 373 gears in mine and it is fine. If you use other than ford gears you can hear a lot of noise. My ford 373 has some noise but nothing I really notice too much. The noise is normal by the way. Unless its over the top, in that case the thing was not put together well.

If you have ever heard detroit lockers in a car nothing after that sounds bad!

When I first put detroit locker in my older car (even though I read they were loud) I was still concerned and took it back to the guy that installed it. He laughed and said "you will learn to love the sound" which I did. The only thing was when you were going around 55 the car seemed to yaw back and forth a little.

Great for the track or strip.

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I had 4.10 gears on my automatic 2005 Mustang GT and it was an awesome daily driver - I put on over 70,000 miles on it before I flipped it. The 4.10's never gave me any trouble - went with Ford Racing and wouldn't recommend anything else. 4.10's automatic will make some nasty launches from the lights, I would do it again.

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I've been reading a few threads on other Mustang forums, and think when the time comes I'll be going with 4:10's.

 

I know it's comparing apples to oranges, but when I had my 1991 Mustang 5.0 with automatic, the big debate was whether to go 3:55 or 3:73. I chose 3:55, and noticed a bigger 'seat of the pants' improvement than any of the bolt on mods I had done to the car. I had no problems at all, and after having them for a while I wished I had gone with 3:73. I had 'feared the gear' and went with the supposedly safer choice, but it felt to me that there wouldn't have been any issues with the 3:73's and the extra over the 3:55 would have made the car just right.

 

So unless I hear a good argument against them, I'll be going for the 4:10's.

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