Upon further investigation, there is no rw sensor that determines speed from the diff. From what I was told, it is all controled by the ECU thru the traction control system.

 

First post here!

Have a blue R/T on order. Had similar thought about gear changes. I doubt that the R/T and the V6 cars use the same differential housing....the torque from the Hemi would likely blow up a V6 rear regardless of the gear ratio. Going to 3.55's or similar would probably kill gas mileage, but maybe 3.23's. I would guess that you probably need the rear gears from a 1500 Ram or similar.

Tire switch is the easy way to go, but smaller tires = less ground clearance, not a good thing. Regardless of whether you switch tires or gears, the computer will be thrown off....not just speedo, but computer now controls tranny shift points, plus traction control, ABS, and a whole list of things we probably haven't thought of that affect drivability. Most times can get away with a small change though.

 

Talked to my contact at the local dealership, who ran the part numbers and such. He said it does look like the housing is the same for all three, but cannot say for sure. Even if, the strengh of the sxt gears are in question. Local aftermarket shop says it would be no problem to put new gears in, I just don't know if it is a 8.25 or 9.25 rear end.

 

Most local shops say "It's no problem" then they put it on and it throws a code immediately. I wouldn't be too trusting unless you have money to burn. I hope someone out there tries this.

 

Won't know until you try........still a ways out here though

 

Well I'm playing with my other cars. By the time I get around to palying with the Magnum, I hope someone comes out with this kind of stuff already. I'm working on the CAI and that's enough for me on the Magnum (for now).

 

I checked with my dealership today re: the tire swap to 225/40 18's. They hooked the diagnostic tool up to my Magnum and verified that the computer allows you to dial in tire changes. The change in wheel size, when fed into the computer via the diagnostic tool, will recalibrate the speedo and alert all other systems to the change so that nothing else (particularly traction control and ABS) is adversely effected.

I'm going with an ultra-high performance all season Pirelli PZero Nero M&S as soon as my checkbook allows it.

Nick

 

SWEAT!!!

Thanks for the GREAT news!!! I'm glad they had the foresight to have that as part of the programming!

 

blackmagnumrt,

Great news and thanks for the research. Going to get my Mag and see how I like the tires. I have a feeling I will be right with you in getting new tires.

This might be a dumb question but what are you using to calculate the circumfrence of the tires and the diference in spedometer. I can do the math manually but if there is an online calculator can you post a link?

Do you know off hand the difference in diameter between the 225/60 and the 225/40?

Thanks

 

Sorry to come off as a math geek, I actually did all of my calculations using the online calculators at Web Car's Auto Math site.

Once you run the tire/wheel compensation calculator, you will be given (among other things) a number that represents the ratio of your old tires to your new ones. So, in order to find the effective gear ratio after the tire swap, you need to plug that number into the following formula:


As to your question about the tire diameter difference between the 225/60 and the 225/40 tires on stock wheels, it is 3.5" smaller (28.6" vs. 25.1").

Happy calculating!

Nick