I'm curious whether the 3.73 (18"wheels) or the 3.92 (20" wheels) rear gears works out better for acceleration. The infamous Road and Track test that obtained such a horrible 0-60 time was on a 3.92, but normally we'd expect more acceleration from the higher numerical ratio. I'm not that into the factory 20" wheels, but might spring for them if that package makes the car noticeably quicker.

 

motortrend got 5.1 sec 0-60 and 13.6 @ 104.9mph in the 1/4mi with the 3.92 manual R/T. I think car and driver as well. i've learned through this and other boards not to go by magazines. 10secdodge has hit some amazing times with his bone stock, granted his is the auto, but his also has the 20 inch wheels though. he got 13.12 in the qtr mile at i believe 108mph. someone else has hit 13.4 stock too. sorry, dont know the guy's name off hand. both have posted slips to prove it too.

 

Correct me if i am wrong. I think the reason they put lower gears with the bigger rims is because when you increase wheel size, the final drive ratio to the ground is higher.

 

The different gears in the 6 speed are due to the tire diameter. As far as the acceleration between the two, it will be almost identical. I have ran 3.91, 4.10, and 4.30 gears in my race car. The only thing that changes is the trap speed (slightly) and the RPM's. The ET is virtually the same.

Lastly... I would not pay any attention to the road tests you read in magazines. There are many people that are getting better times out of their stock cars than the rags. You best bet is to test drive one of each.

 

Plus the Mags might be testing new and tight cars or completely ragged out test mules. The mag cars vary widely and you really don't get an accurate result. The motorcycle journos are the worst. Most of them aren't really that experienced at racing but they can write and punctuate properly so they get the job. The Challenger is the baddest 4000lbs HEMI powered car on the road. And guys, 1/4 mile sprints just kill a drive line. Each pass probably causes hundreds of tiny hair-line fractures in everything from shafts to crank journals. This happens over the life of any car anyways but drag racing just accelerates the crap out of the process. Sure, I'll plant my foot on an occasional pulse quickener but mostly I cruise it around counting the thumbs-ups. I guess I should be thankful to you guys. With you out there proving what these cars can do, I can just repeat your results to any Mustang/Camaro head and settle it without stressing my car. Cool. I take it all back.

 

Rim diameter does nothing to determine the proper rear gear. It is the overall tire diameter. And for that, the differnce is negligible as seen in the diameters I got of the Tire Rack website for the stock 18s and 20s...

235/55 R 18s....28.4 inches or 731 revolutions per mile
245/45 R 20s....28.7 inches or 729 revs per mile

Not enough of a difference to require a gear change from 3.73 to 3.92.

The lower (numerically higher) 3.92:1 gears are for performance only (and just maybe to move the extra heft of the heavier wheels).

But traction is a limiting factor when using the lower 3.92s. The wheels will accelerate faster which could lead to more spin and slower times if the driver is not careful.

 

Cool, well it sounds like I don't really need the 20's then.

 

I think you need 20s and 3.92 gears in order to get the posi rear, however

 

From what I could tell all 6spds got the limited slip.

 

When you go to build the car online, and select the 6 speed (with 18" wheels selected) it says:

Includes the following:
Anti-spin differential rear axle
Bright accelerator, brake and clutch pedals
Hill start assist
Performance Steering
Track Pack