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Discussion Starter #1
I have a 2010 challenger r/t 5.7L, do I have limited slip or open dif (uni traction) would i need to upgrade to limited slip and at what gear ratio? i'm looking for better take off, would a lower gear help?
If so who makes differentials or gears for my car, someone please help :) Thanks
 

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If your R/T is an automatic you have the "open" differential with the 3.06 final drive. This is the 215mm ring gear Mettingen model

The max ratio recommended for automatics is a 3.55 gear since the top gear is .83 for automatic.

If you have the 6-speed stick, your car would already have the Sure-Grip (limited slip) 226mm Getrag with.
*3.73 with 18" tire/wheel
*3.91 with 20" tire/wheel

The stick versions get lower gearing since they have two overdrives and 6th is pretty tall gearing @ .50 / 5th is .74 gearing.

The upgrade to limited slip would require the 226mm differential as there's no provision for limited slip with the smaller 215mm diff available.

(The automatic '09-'11 SRT8 gets a Sure Grip 226mm Getrag, but only with 3.06 gearing) 'Stick version gets the 3.91 gearing & Sure Grip on SRT8.
 

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Discussion Starter #3
thank you

my R/T is an automatic, if I ger the 255mm LSD would the 3.55 ratio still be the max i can uae?
 

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09 RT Challenger auto
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I just installed a gettrag, I stayed with the 306 gear. I use 1st 2nd 3rd 1/4 mi
They make a LSD called, qualife that fits our 215 rear for autos as you have. It has 306 323 355 gearing for it I think. If I didnt get a deal on my 1000hp axels and gettrag combo I would of went that way. It cost around 800.00 for the LSD.. Keep your 306 and install a 3000 stall converter. Youll have take off,,alright, and still cruze highway well.
FT
 

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my R/T is an automatic, if I ger the 255mm LSD would the 3.55 ratio still be the max i can uae?
Most recommend 3.55 as the max for the automatic - 1st gear is low on these and there's the hit on fuel economy to factor in as well. You'd be close to 3k rpm (or more?) at highway speeds - that's a lot of wear and tear if you went with a 3.73 rear end + automatic.
 

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Most recommend 3.55 as the max for the automatic - 1st gear is low on these and there's the hit on fuel economy to factor in as well. You'd be close to 3k rpm (or more?) at highway speeds - that's a lot of wear and tear if you went with a 3.73 rear end + automatic.

I just put the 3.91 in my 09 SRT8 auto and love it. RPMs @ 80 mph is 3050 and at 70 mph it is 2750. First race yesterday it picked it up from last years best of 13.6 to a P B of 12.71 Its Awesome,Luv It!!!!!!!!!!!!!
 
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