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Discussion Starter #1
Folks, I have a 2007 SRT Charger with the NAG1 tranny and the 3.06 Getrag gear. What is the expected engine RPM at 70MPH if I install the Getrag 3.73 gear? I want to know what tio expect if I install a SC 392 with the 3.73 gear to dterrmine engine longevity.
Thanks
 

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If I remember right I run about 2100-ish. For an exact number I'm sure there are formulas on line for the calc's. Or, Eddie or Builder Bill could tell ya.
 

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with 28" diameter tires in fifth gear you will be going 2600rpm to go 69.95mph
Man, I didn't think it was that high. I smooth out at about 1500-1700 and the exaust quiets down at about 2000 and that's around 65. I am running 315/35's, the 3/4 inch might make a difference.
 

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I'm sure your right GSO. i haven't had her out for about 4 months.
 

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Man, I didn't think it was that high. I smooth out at about 1500-1700 and the exaust quiets down at about 2000 and that's around 65. I am running 315/35's, the 3/4 inch might make a difference.
It's higher even than GSO said. If you wanna know what it feels like drive around in 3rd on the highway.
 

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Folks, I have a 2007 SRT Charger with the NAG1 tranny and the 3.06 Getrag gear. What is the expected engine RPM at 70MPH if I install the Getrag 3.73 gear? I want to know what tio expect if I install a SC 392 with the 3.73 gear to dterrmine engine longevity.
Thanks
QUOTE=gsochallenger;702508]with 28" diameter tires in fifth gear you will be going 2600rpm to go 69.95mph[/QUOTE]

GSO is about spot on for my ride when I run the DR's and I've been running the 3.73's for over 2 years now!!
For Street and show I run a 285/40-22 (31" Diam) which brings the RPM down even more....But to tell ya...the 2500 isn't bad....my '01 Lexus Is300 runs about 2700 RPM at 70....I have 400,000 miles on the original car!
G
 

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I used the stock converter, for now. In that regard i have "lock" sooner rather than later. Honestly there are a lot of things I'm looking forward to dialing in this coming spring/summer. Cooling, suspension, hook up, launch.... etc...
 

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I used the stock converter, for now. In that regard i have "lock" sooner rather than later. Honestly there are a lot of things I'm looking forward to dialing in this coming spring/summer. Cooling, suspension, hook up, launch.... etc...
No you don't actually....they all "LOCK" at the same points.....this is not the same as stall. On a stock tune the converter doesn't actually lock 100% either and this is what I meant by percentage of lock up.
 

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No you don't actually....they all "LOCK" at the same points.....this is not the same as stall. On a stock tune the converter doesn't actually lock 100% either and this is what I meant by percentage of lock up.
Got it. Good to know. Thanks
 

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Discussion Starter #16
Thanks for all of the responses folks as this information will help me determine whether I will move to the 3.73 in the Charger. Appreciate the follow-up questions/comments. Clearly I have much to learn and the members of the forum are a wealth of knowledge.
 

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Discussion Starter #18
You will have a 21.9% increase in rpm from your current readings.
Ok, there is a mathematical formula out there some where that allowed you to obtain this value. Can you provide the web site?
 

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I'm sure there is but it is just basic mathematics. 3.73 is 21.9% larger than 3.06. In reference to his query his engine will rev 21.9% more than it does now with all things being equal.
 

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I'm sure there is but it is just basic mathematics. 3.73 is 21.9% larger than 3.06. In reference to his query his engine will rev 21.9% more than it does now with all things being equal.
True but thought there may be a formula that includes effect of tire diameter on rpm. I should have been more clear in my question.
 
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