I'm a little confused about what exactly the 3.92 that is in my TRX4 means and why its a good or bad thing? So higher # 4.56 puts out more torque at a given RPM range? So this will help my mileage for city driving but hurt it on the highway? And the 3.92 is kind of like the middle ground between performance and mileage? I heard that getting new tires such as a 33" or 35" can have a different effect depending on your gearing.

 

Higher (numerically) gears give you low end torque good for towing and burn outs... but higher rpms and lower mileage at hi-way speeds... I have factory 3.92s and turn 2k rpms @70 mph w/20" wheels,

 

3:55 would be considered "Prairie gears" with weak low end torque but able to keep rpms low on highway. 4:56's are considered "drag/towing" gears as they alter the torque curve and produce power at slower speed(because they make the engine rev more) and produce power instantly because the rpms are kept in the powerband but they rev very high when traveling on the freeway.
Your 3:92's are in the middle and are good for 33" rubber and mild towing to get best of both low end torque and reducing highway rpms.
3rd Gen Hemi's produce more power and achieve better mpg's when rpms about 2200 at crusing speed. So, you could actually go to 4:10's get better mpg's(hardly even noticeable) and slightly better torque curve(not very noticeable either)

 

It's the ratio of complete driveshaft revolutions to a single axle/wheel rotation. 3.92:1 ratio would mean the driveshaft turns 3.92 times completely around by the time the wheel makes one complete rotation. Anything other than that is personal preference and compromise.

 

Ok so for mostly city driving ( unfortunately for now ) The 4.56 would be better or as you said the 4.10.. Awesome, probably gonna be a while before I change anything. Don't really have $1800 sitting around once my tires and exhaust are bought haha.. Thanks for the help guys!

 

I wouldn't change a thing if I were you. Except if you have a factory LSD out back, then stick in an Auburn or DTT instead.

 

I wouldn't change anything either. Unless you are doing a very specific task that you are struggleing with you probably wouldn't be able to justify the cost versus the reward for the swap.

 

^^^X3. Unless you have a real heavy foot, shares in a tire company or haul a big trailer, the 3.92/4.10's are a good range. Now if you increase your tire diameter by 10-20%, then 4.56 might be nice to bring you back to stock performance but otherwise, keep the $1800 and buy some other toys.

 

I don't do any hauling or own any tire company shares so looks like I'll completely forget about the gearing haha. Pretty much exactly what I wanted to hear! Thanks for the help

And gonna slap some 33"s on there in the next week or so. I want BFGoodrich KM2s or possibly the KM or Nitto Trail Grapplers. You guys have any opinions on which of these tires over the other.. Gonna be about 75% on road 25% off road

 

It really depends on what "off road" means to you. And, your personal preferrence, to looks or function.