2009 R/T axle ratio
 

So what are the options? If I go to build one on Dodge's site it doesn't seem to say either way now.

Is the auto still a 3.06? Seems like when I went to go build one a few months ago the site was different and indicated 3.92 for the manual and a 3.72 for the auto. But now it doesn't say either way.

RE: 2009 R/T axle ratio
 

There were some issues I noticed with Dodges website early on. It should be: Auto 3.06 only with the manual getting 3.72 with 18" rims and 3.92 with 20" rims.

RE: 2009 R/T axle ratio
 

Cuda, that is what I understand as well. The look of the website did change substantially a while back (few weeks I think, but maybe longer).

RE: 2009 R/T axle ratio
 

Why is there a difference between the axle ratios and the 18" & 20" rims?

RE: 2009 R/T axle ratio
 

Most likely because the overall wheel and tire is taller on the 20" than on the 18", thus making the final drive higher (numerically lower).

RE: 2009 R/T axle ratio
 

I check Tirerack for specs. Goodyear F1 P245/45/20 28.7" overall diameter optional tire comes on car
Pirelli Scorpion P245/45/20 28.6

Goodyear Eagle RS-A P235/55/18 28.0
Michelin Pilots HX P235/55/18 28.4 overall diameter standard tire comes on car

Not much of a difference .3 of an inch.

RE: 2009 R/T axle ratio
 

With the manual trans, you can opt for the 20 inch wheels, the 3.92 gears and the only way to get a limitted slip differential and the only way to completely disable the traction control. I know this from plenty of discussions with Dodge dealer sales and tech reps.

The 3.92 probably overcomes a bit of the "loss" of performance form the larger and presumably heavier 20 inch rims. The traction control on the other models can be disabled, but not completly, apparently in order to make up for the lack of a limitted slip, the traction control will possibly partially prevent the one-wheel-spin at launch.

The overall tire height diffence should not be enough to require a different ratio to match up the speedo for 18 or 20 inch rims. As indicated by Dodge Farve Ever, the difference is small, and most manufacturers try to keep the overall tire height difference within neglegible limits for ease of swapability (dealer upgrades).

(Removed references to Trak-Pak)

RE: 2009 R/T axle ratio
 

The Trak Pak will get you the 20 inch wheels and 3.92 gears only if you opt to pay extra for it on top of the Trak Pak. The Trak Pak alone gets you the 18" wheels.

RE: 2009 R/T axle ratio
 

Ripetide, the automatic's axle ratio is a 3.06 and the manuals is 3.73 for 18 inch rims and 3.92 with 20 inch rims. To put this into perspective the gear ratios for the automatic are as such:

1st 3.59, 2nd 2.19, 3rd 1.41, 4th 1.00, 5th .83

for the TR-6060 it is as such:

1st 2.97, 2nd 2.10, 3rd 1.46, 4th 1.00, 5th .74, 6th .50

This makes the difference in gearing much closer after calculating these together. You will find that the gearing is quite close but ultimately favors the manual.

RE: 2009 R/T axle ratio
 

This thread has some good info. The tire diameters is very interesting and the transmission gearing is helpful too. This is the kind of stuff that keeps me coming back. Thanks. RLSH700, I was wondering if you could share the math involved with figuring the final drive ratio when considering the overdrive ratio of the transmission? I think you stated in another post that the final drive ratio of the automatic with 3.06 gearing is actually 3.79 and I can't understand how that can be. I would think that the overdrive would cause the final ratio to be a lower number, I mean less than 3.06 not more. I really would like to see the math and see what you mean. I'm not doubting you but I want to learn something here.