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Dodge Magnum The Dodge Magnum, the wagon that made wagons cool. The unique look of the Dodge Magnum makes any trim level, from SE to SRT-8, an absolute head turner.

Rear End Gears

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  #1  
Old 07-09-2004, 08:54 PM
BlackRT BlackRT is offline
 
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Default Rear End Gears

I am anxiously awaiting my factory ordered Black RT. I had Corvettes and recently sold my last one, a 96 collectors edition LT4 6speed, in favor of my 03 chevy truck that seats a few more people. Man, do I miss that vette. Trucks suck. No handling, no speed. Long story short, I drove the RT and it was the best of both worlds. I can't wait for mine.

My first noobie question...It seems to me that the easiest way to get some additional performance out of the RT would be to step up the gearing in the rear end. 2.82 seems really tall, especially with a 5 speed auto. Jumping up to around 3.5 would really give it some acceleration. Anyone know anything about this? A supercharger is on my list but I think we'll be waiting a little while for that one.

Thanks
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  #2  
Old 07-09-2004, 09:52 PM
BubbaG BubbaG is offline
 
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Default RE: Rear End Gears

There should be no problem getting the gears from the V6 models. 3.46 and 3.90's i believe. But no confirmation as of yet if they are the same.
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  #3  
Old 07-09-2004, 10:26 PM
BlackRT BlackRT is offline
 
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Default RE: Rear End Gears

Yes. I am hoping that using the gears from the SE or SXT will be possible. I guess this is assuming that all three models use the same diferential. I was disapointed that a rear end ratio wasnt an option.

On a similar note...Does anyone know the gear ratios for the 5 speed auto? I'm trying to calculate the pro and cons of a gear swap.
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  #4  
Old 07-10-2004, 12:47 AM
BubbaG BubbaG is offline
 
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Default RE: Rear End Gears

5 speed gears are
1st - 3.59
2nd 2.19
3rd - 1.41
4th - 1.00
5th - .83

Rear gears available are
2.82 (r/t)
3.64 (sxt)
3.90 (se)
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  #5  
Old 07-11-2004, 02:49 AM
phantom505 phantom505 is offline
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Default RE: Rear End Gears

I wouldn't be swapping the rear ends out with the V6's without having it checked out first. Mostly because I bet the axels aren't strong enough as is. It just means we will probably have a blue print to work off of, but we will have to get the computer redone too. And who knows how hard it will be to reprogram this computer....
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  #6  
Old 07-12-2004, 06:03 AM
blackmagnumrt blackmagnumrt is offline
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Default RE: Rear End Gears

I agree with the others who have concerns related to the strength and suitability of the gears from the SE and SXT. I have another possible solution though...

As I have said elsewhere on this forum, with around 5000 ticks on the odometer, I am completely dissatisfied with the stock Continentals on the RT. My biggest beef is their tendancy to hydroplane (especially the fronts) in heavy rain. This does not bode well for winter handling. A quick search of the Tire Rack's inventory shows that the only tires in factory size are, you guessed it, Continentals. However, stepping down in aspect ratio to a 225/40 gives you an entire range of good tires (including ultra high performance all seasons). The 225/40 aspect ratio also effectively changes your gear ratio to from 2.82 to 3.21 (225/40's go from a circumference of 89.94 inches to 78.81 inches) which should provide noticable low end boost. Now this does not effect true hp or torque numbers but math is math and the effect is the same. This will lead to a speedometer that reads 56.9 when you are going 65 but that can be corrected.

Any thoughts?
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  #7  
Old 07-12-2004, 06:37 PM
BlackRT BlackRT is offline
 
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Default RE: Rear End Gears

Swapping out the tires is a great idea. Especially if the speedometer is recalibrated easily. My only concer would be the stance of the Magnum. It has such massive wheel wells as it is I would hate for there to be even more space.

As far as everyone's concern with the rear end wap out here's my thoughts...It is my guess that the rear ends are all the same, just the gearing is different to make up for the lack of torque from the smaller engines. So swaping out the gears should be easy. As far as reprograming the computers...I think that this should be unnessesary other than the speedometer. Swapping out tires makes a big diference as blackmagnumrt pointed out previously and no one would worry about computer reprograming after they slap on the set of dub.

So other than strength and compatibilty issues I think a gear change would be very easliy done.

One other thought and I haven't done the math at all...but are the rear end gears actual or might they be the same gear and then calculated based on tire diameter? Something to think about.
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  #8  
Old 07-12-2004, 07:19 PM
BubbaG BubbaG is offline
 
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Default RE: Rear End Gears

Quote:
ORIGINAL: BlackRT

Swapping out the tires is a great idea. Especially if the speedometer is recalibrated easily. My only concer would be the stance of the Magnum. It has such massive wheel wells as it is I would hate for there to be even more space.

As far as everyone's concern with the rear end wap out here's my thoughts...It is my guess that the rear ends are all the same, just the gearing is different to make up for the lack of torque from the smaller engines. So swaping out the gears should be easy. As far as reprograming the computers...I think that this should be unnessesary other than the speedometer. Swapping out tires makes a big diference as blackmagnumrt pointed out previously and no one would worry about computer reprograming after they slap on the set of dub.

So other than strength and compatibilty issues I think a gear change would be very easliy done.

One other thought and I haven't done the math at all...but are the rear end gears actual or might they be the same gear and then calculated based on tire diameter? Something to think about.
The gear numbers would be actual, not calculated based of tire size.
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  #9  
Old 07-12-2004, 08:08 PM
Robb03 Robb03 is offline
 
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Default RE: Rear End Gears

You shouldn't have to recal the speedometer with the mangum's gear change, assuming it has antilock brakes in the rear. My 01 dakota is going to get new gears real soon, and the sensor that determines the speed of the axle resides in the right hand part of the differential. You can change to any gears, and it reads the correct speed. Tires are a different story......
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  #10  
Old 07-12-2004, 09:17 PM
phantom505 phantom505 is offline
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Default RE: Rear End Gears

I wouldn't count on us having the same system. As far as I can tell our car isn't even that close to the HEMI Rams.
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  #11  
Old 07-13-2004, 02:36 PM
Robb03 Robb03 is offline
 
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Default RE: Rear End Gears

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.
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  #12  
Old 07-13-2004, 04:44 PM
HemiGuy HemiGuy is offline
 
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Default RE: Rear End Gears

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.
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  #13  
Old 07-13-2004, 04:54 PM
Robb03 Robb03 is offline
 
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Default RE: Rear End Gears

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.
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  #14  
Old 07-16-2004, 12:09 AM
phantom505 phantom505 is offline
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Default RE: Rear End Gears

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.
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  #15  
Old 07-17-2004, 12:04 AM
Robb03 Robb03 is offline
 
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Default RE: Rear End Gears

Won't know until you try........still a ways out here though
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  #16  
Old 07-17-2004, 12:16 AM
phantom505 phantom505 is offline
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Default RE: Rear End Gears

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).
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  #17  
Old 07-21-2004, 09:57 PM
blackmagnumrt blackmagnumrt is offline
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Default RE: Rear End Gears

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
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  #18  
Old 07-21-2004, 10:12 PM
phantom505 phantom505 is offline
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Default RE: Rear End Gears

SWEAT!!!

Thanks for the GREAT news!!! I'm glad they had the foresight to have that as part of the programming!
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  #19  
Old 07-22-2004, 07:18 AM
BlackRT BlackRT is offline
 
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Default RE: Rear End Gears

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
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  #20  
Old 07-22-2004, 02:13 PM
blackmagnumrt blackmagnumrt is offline
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Default RE: Rear End Gears

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:

original gear ratio (in this case 2.82 for the R/T) x ratio of old tires to new (in my example 1.14) = effective gear ratio (3.21)

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
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Old 07-22-2004, 02:13 PM
 
 
 
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