AC gears vs. Calmini gears

[superslidestyle]

I've noticed that even with all the work I've done on my Xterra, I'm having a hard time maintaining my freeway speed in the fast lane only when I go uphill.  Would upgrading to aftermarket diff gears help with the extra gear weight and taller 31" tires?

What is the advantage of one vs. the other?  3.92 (Camini) vs. 4.88/5.142 (AC)?  What is the OE ring gear size? 

Who has them and what has been your experience with them.  Does it make your gas milear get better. I'm currently getting 12/14 mpg.

[SCsilverX]

how are you getting 12/14? I was running 33's and getting 15. maybe take your lights off when you arent offroading.

[superslidestyle]

I dunno.  I know I need a new fuel pump and new cats.  Car seems stronger now that I upgraded the exhaust but I could use a bit more bottom end power from 2000 to 3500 rpm.  Above 3500 rpm feels fine.  Thinking about getting the Jet ECU reflash also.

[Bobby B.]

First off, the gears to which you are referring are 4 lo crawler gears.  Won't do a thing driving down the road.

Secondly, you have a bigger problem than your current diff gearing if you can't drive at speed on the freeway. 

[superslidestyle]

My X drives fine for a normal driver but I tend to have a heavy lead foot and I'm used to driving sports cars.  My wife has a Nissan Murano SE AWD with much quicker acceleration and makes 285hp.  It would be nice if another Xterra owner would drive mine to get a second opinion of the cars performance.

The gears I'm talking about would be for the rear diff.

[Bobby B.]

Again, the 3.92 gears you mentioned are low gears for the transfer case.  Won't do a thing for you.

The lower AC gears (higher numerically, like 5.14) will give more low end grunt from a stop but not help on the highway.  Not with 31s, the size which came stock on many, if not most xterra models.

[superslidestyle]

So what would you recommend?  Is this a feasable project?