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i have a mechanic buddy that told me that by swapping our 2.73 for a moderate ratio like a 3.23 we'd definitely improve performance without sacrificing much in fuel economy..what are your thoughts?? also, given such a swap how much would our ET DROP??? thanks :)
 

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I'd do 3.55's right now if they made them. You can't just change gears though, you need a software fix for the speedo....so it may be awhile before this could come available.

Gears will be the biggest SOTP gain you can do(.) - No HP gains, but good for maybe .3/10th's as the car will get out of the hole and into the rpm's quicker (may lose some trap speed though).
It was by FAR the most noticebly mod I've done to my stang.

I'm patiently waiting....
 

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You sure you can't do it without a software change? (Speedo) It depends if the speed sensor was on the imput side of the shaft or the output side... If it was on the output, then we'd be fine.... If you can spin the tire on one side and get no speedo reading, then you're in luck..... Although, one has to wonder how far we could go, or even if the computer watches speed to rpm relationships...

I might be getting ahead of myself there...

But, any performance shop looking to make some quick cash could come out with a gear set for the 300C/Magnums... It would help them seem about 400lbs ligher...
 

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Good question, on my 94 stang, my speedo just needed a different speedo gear, but it dropped my rev limiter from 6k to 5500k rpm when installing the 3.73's from the stock 3.23's as the speed sensor and speedo guage are diffreent. I was bouncing off the limiter at WOT between the 1-2 shift...talk about a HUGE issue, falling flat on it's face in between shifts....It took a chip to fix and raise the rev limit.
Also, any of the new style stangs 99' and up need a special inline add-on to fool the computer and give the speedo correct read out as there are no speedo gears like in my 94.

I don't know about C, but with all the computers in the C - I'm sure it's not just a simple fix. I know the dealer can adjust for different wheel sizes up to 18 inch for speedo correction....so that logically tells me its all computer ?
 

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Yup! You are correct... Most of chryslers car use the speed sensor system and in their programming tool they tell the car what tires are on it.. Normally just fixed to OEM sizes, but that can be changed.. It's a pretty common thing on truck programmers to be able to program in different size tires. I know when the PT got it's ECU replaced, they forgot to program in the tire size completely, and the speedo didn't move, I was prepared for that and checked right away when I drove it out. Gotta love the online forums!
 

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You should be able to get a rear end out of a wreck 2.7 300 or magnum and swap out the unit. I know that the electronics have changed but the delears use to be able to change the (pinion factor) based on tire size.
 

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About the differentials in our 300C's and Magnums....the 2.7, 3.5, and 300C/RT AWD Hemi's have Mopar 198RII differentials, while the 300C/RT has a 210RII. I think the number is the ring gear diameter in mm. Anyway the 198RII comes in 3.08, 3.64 and 3.90 and the 210RII only comes in 2.82. (You 300C and RT AWD folks could spend a fortune and upgrade X2 to 3.64 or 3.90....$$$$$) For now it looks like rest of us are out of luck for better gearing. I would like something around 3.42. Years ago I use to race Oldsmobiles, (because everyone had Chevys.) with the early 4 speed hydramatic. It had similar gear ratios to our 5 speeds. The 300C and RT 1st thru 5th ratios are, 3.59, 2.19, 1.41, 1.00, and OD .83. The early hydramatic was 1st thru 4th was 3.82, 2.64, 1.42, and 1.00. I could run as fast with a 3.08 differential using 1st, 2nd, and 3rd as I could with 4.56 gears using all 4 gears. I use to calculate the overall ratios and compare with the Chevy's 4.56 and 4 speed manual. With the hydro. the ratios were still better. My point is, we're not too bad off now, but 3.08> would be better. I calculated our 300C/RT's (2.82) and compared to the new Mustang GT (3.31) with their 5 speed manual.
Mustang overall 1st thru 5th is 10.75, 8.07, 5.13, 3.31, 2.48.
300C/RT overall 1st thru 5th is 10.12, 6.18, 3.98, 2.82, 2.34.
We're hauling more weight, but have more torque and horsepower. BOTTOM LINE: GEARS WOULD HELP.
 

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So what rear end does the SRT-8 have on it? Hmmmmm.....
 
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