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Discussion Starter #1
I'm sure there has to be previous posts on here somewhere, but they didn't pop out at me. I believe our stock 06 RT even w/ R&T pkg came equipped w/ a 2:73 rear end gear, which is pretty tame by any standards. I'm guessing they did this to achieve a fuel economy rating. I would like a performance boost with minimal effect on miliage.. how about a 3:08 or equivellant? Has anyone done this yet, and if so, how much mpg did you lose?
 

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I could be wrong, but I thought the R/t already has the 3.08?:4-dontknow:
 

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Discussion Starter #6
Shortly after getting this car I called Chrysler's Support Line, gave them my VIN, and they sent me the Build-Sheet with everyhting that went into it. I just looked it up to re-check, and I was incorrect. The Build Sheet lists it as "2.82 Drive Axle" (Build Code-DMBS)
 

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So for those of us that are still learning, does anyone care to explain further what you guys are all talking about? I'm quite curious...
 

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There's a ring gear and a pinion in the rear differential. The ratio 3.08 means 3.08 revolutions on one end (the drive shaft) equals 1 revolution on the other side (in this case the output shafts connected to the rear wheels). The higher the gear ratio means more power, less speed. I put 4.11 gears in my jeep for more power to climb hills and such. Lower gear ratio means higher speed but you have to have the power to push at high speeds. I've seen some race cars that were geared so low they had to be push started to get rolling but they go 200 something miles an hour. Does this all make sense? From what I understand, they don't make replacement rings and pinions yet for our cars. You can upgrade an R/T to an SRT rear differential but you have to change the output shafts as well. I know an ebay seller that has both the diff and shafts for a total of like $1400.
Stubbie68
 

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Thought I would explain a little more if you don't mind. I'm on a roll.
Have you seen the Quaife locking differential for sale? I've seen it for about $1500 alone. Well that's the center section that the ring gear attaches to. The output shafts on either side attach in the middle. Well, when power is applied the Quaife locks both rear wheels together so power is applied evenly to both wheels. Without one (called an open differential) exactly what we have in all our stock Chargers, when power is applied and one wheel slips (looses traction) all the power you're puttin out goes to the tire with no traction. With the Quaife, if you loose traction on one wheel, the other is still gettin 50% of the power. Better traction, faster take off.
Standing behind your charger facing the trunk. The drive shaft and pinion turn clockwise or counter clockwise (forward or reverse) which makes the ring gear turn so that the top of the gear is moving towards you or away from you just like the tire rotation. Does that pull it all together for you? If you have questions just ask.
Stubbie68
 

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So if I go a bigger gear I get more power but a lower top speed? Is that correct? So if that is the case than a larger gear will better my track times?
 

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So if I go a bigger gear I get more power but a lower top speed? Is that correct? So if that is the case than a larger gear will better my track times?

Navy Charger,
Correct. The higher gear will allow the motor get into a higher horsepower range quicker and that is actually where the "power gain" is. Top speed decreases (engine is spinning faster now to spin that gear one revolution - 3.08 times per rev compared 2.82 per rev). You actually 'run out of gear' on the top end (RPM is so high the car won't go any faster)

Absolutely better track times. But it's all relative of course (our motors don't make big power on the top end so too big of gear and the car will be slower.)

Hope that helps.
 

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So if I increase my top end (not sure how to do that by the way, I could go with a larger gear than 3.08 and make even more power to the wheels? What would that do to the HP loss from the crank to the wheels? Would that mean that I am closer to the 350 that the engine is pumping out at the wheels?
 

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I've been told SRT8 Jeeps are running 3.73 gears and they animals on the track.

I will tell you from experience with other cars, being able to change to this gear alone will make a HUGH difference with no other mod to your car. I would not go higher though (drivability will start to become an issue on the highway)

Food for though:
If you are @2200 RPMs @65 mph now, you could easily add 800 to 1000 RPM by going to that gear @ 65mph.
 

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So if I increase my top end (not sure how to do that by the way, I could go with a larger gear than 3.08 and make even more power to the wheels? What would that do to the HP loss from the crank to the wheels? Would that mean that I am closer to the 350 that the engine is pumping out at the wheels?

Changing gears will never increase the HP at the wheels. It will only allow to get to your peak rear wheel HP your car already has quicker. Engine modifications are the only things that will increase HP/TQ
 

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so instead of being at 2200 @ 65 I would be cruising at 65 wirh 3000-3200 RPM?
In theory yes. There are equations to figure this out but you need the final trans gear ratio and the rear gear ratio tire size etc. to be exact.

example:
I had 3.27 in my mustang, went all the way up to 4.11 and that added 1000 RPM to my cruising speed on the highway.
 
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