General Challenger DiscussionThis section contains general discussion about the Dodge Challenger. If it does not fit into a more specific area, it probably belongs in here. (Dodge Challenger General Discussion)
OK for those in the know I have a few questions ..
auto has 373 rearend gearing & the Manual has 392 . Why the difference ?
Also I have a manual Rt, 20 in wheels 392 gears .. If I was to go to say 18 or 17 in rims would this make the car rev higher & or have a positive effect on 1/4 mi speeds ??
All autos have 3:06 gears.
Manual R/T with 18" wheels get the 3:73.
Manual R/T with 20" get 3:91.
All SRT manuals have 3:91.
The rev limiter won't change.
Smaller diameter tires would give a lower final drive ratio that would help in the 1/4 mile time.
OK for those in the know I have a few questions ..
auto has 373 rearend gearing & the Manual has 392 . Why the difference ?
Also I have a manual Rt, 20 in wheels 392 gears ..
The 20" stock tire size is .5 taller
(90.1" circumference / 28.7" diameter / 703 revs/mile)
than the 18" size
(88.5" circumference / 28.2" diameter / 716 revs/mile)
so comparing the stock tire sizes, the 3.92 gear offsets the loss of effective ratio with the taller 20" tire, so it works out the same as the 3.73 gearing with the shorter 18" tire...
You end up with the same overall ratio - it was done to keep the speedo and rpm/mph the same with the 6-speed setup.
The 3.06 & automatic is used whether the car is equipped with 18" or 20" wheel / tire setup. Its likely MDS (on the 5.7 R/T) offsets the change in effective ratio, so Chrysler didn't bother with different gearing on the automatic setup.
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2009 R/T 27J pkg (6 speed MT) ordered 7/17/08, built 10/23/08, home on 11/13/08
it's not the wheel size but the overall diameter of your rear tires which will reduce your overall ratio.
just get rear tires with a smaller diameter and you'll reduce the overall ratio.
Thanks guys certainly clears things up ..
Imagine putting a 15 in rim w/ 255 x 60 tires .. Certainly would reduce the gear ratio .. But it would look hideous given the enormous wheel wells these cars have .. I guess the only way to change the gear ratio is by actually changing the gears .. ( makes sense )
doing that this fall to my 66 GTO .. Guy i bought it from 10 yrs ago had 3.08s in there .. after restoration ( just completed & broke ) going to go with 3.73 .. Ought to give it some snap huh ?
Had 3.93 gears in my 72 Nova SS when I was a kid .. That thing use to really go ...
Imagine putting a 15 in rim w/ 255 x 60 tires .. Certainly would reduce the gear ratio .. But it would look hideous given the enormous wheel wells these cars have .. I guess the only way to change the gear ratio is by actually changing the gears .. ( makes sense )
doing that this fall to my 66 GTO .. Guy i bought it from 10 yrs ago had 3.08s in there .. after restoration ( just completed & broke ) going to go with 3.73 .. Ought to give it some snap huh ?
Had 3.93 gears in my 72 Nova SS when I was a kid .. That thing use to really go ...
At the track, I often see the LX guys (Magnums and Chargers) running 18's on the rear (esp if they have the SRTs which get 20" wheels std.) to get more lower final drive since they may have 3.06 or even 2.81 diffs, depending on the model year...
I'll be that Nova's engine with the old 1:1 top gear (auto or stick) will probably be spinning somewhere between 4 - 4.5K rpm at highway speeds!
Great for the track, but horrible for mileage and just the engine noise trying to drive it on the street. Some folks even went with lower gearing (4.56 or more), but at that point is just a track toy after that - not usable for daily driving.
Fwiw, the torque multiplication effect in the fluid coupling of the automatic is essentially like a 1.25-ish gear reduction (varies according to engine load). So that 3.06 axle ratio is effectively like a 3.825, in conjunction with the automatic transmission properties. 1.25:1 being conservative, the effective ratio could end up even shorter than that.
Now, if the transmission activates lock-up clutch mode, then the effective ratios and axle ratio work as you expect they would (at a constant cruise on a city street or the hwy). I don't think it typically enters this mode if you are racing the thing, though.
It's not that I really needed 370 hp...but having 150+ hp riding shotgun at a moment's bidding w/o a 6000 rpm moonshot is what makes me feel like I'm in the right car for me. The roar of a v8 seals the deal!
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Last edited by randycat99; 07-26-2010 at 02:30 PM.
You may also want to keep in mind when you mess with the tires sizes for the sake of changing gear ratios, you also mess with speedometer accuracy and in turn actual mileage on the odometer in the long haul. Granted it's not at all bad when you raise the GR but you lower it you're actually piling on more than the actual miles traveled.
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