I have a 1998 4x4 4.0L OHV
It came stock with 3.73 and 235/70/R16 = 29.0" tires
Right now it has 3.73 gears and 265/75/R16 = 31.6" tires
It seems to be making the torque converter do too much work and my highway mileage isn't any better since my driving is not a "steady 65" in which case these gears would do good.

So I am thinking of regearing but can't decide between 4.11 and 4.56 gears.

Looking at this chart and approximating the rpm values for the 31.6" tires I end up with these values.
http://www.4lo.com/calc/geartable.htm
multiplied by 0.75 to account for OD at 65mph

3.73 - 29.0" - 2107 rpm
3.73 - 31.5" - 1940 rpm
4.11 - 31.5" - 2137 rpm
4.56 - 31.5" - 2372 rpm

Stock:
Max BHP = 160@4200rpm
Max TQ = 225@2750rpm

Now I see that 4.11 gears would set my truck back to around stock but with the higher rotational mass and rolling resistance of the tires I was thinking of going to the next step up. I am just worried that it would be too over-geared however it is closer to and still below the max TQ rpm. Most of the driving I do isn't on the highway so I would like a little better pep and acceleration through town. Is there anyone else running this setup, do these figures seem right?

 

I went from stock 27.4's with 4.10's to 31's and 4.56's. Its close to stock but honestly wish i would have gone with 4.88's.Im in the same boat as you most of my driving is city.Geared and tuned im getting a max of around 15 Mpg's city if i baby it and around 22 Mpg's hwy.I would glady sacrific a few Hwy Mpg's for a few more city Mpg's.IMO go with the 4.56's if you dont like it bump up to 33's down the road.

Edit: try this calculator
http://www.superioraxlegear.com/calc...re-height.html

 

Do you have a 4 cylinder of something because that gearing seems really high to start with?
That calculator was nice, I just wish it was .75 overdrive but it gives me a good enough idea.

 

Does anyone know what the front diff is in a 1998 4.0 ranger, Iknow my rear is a 28 spline 8.8" but what is the front, a dana 28 or dana 35?

 

Well I think I am just going to go with 4.11 gears to set it back to stock. Does anyone know a good place to buy gears?

I found these, Are they the right ones and is this everything I need?
http://completeoffroad.com/i-369355-...deal-4-11.html
The front one is the one I am really unsure about, it seems like it is for a jeep, would the install kit work?
http://completeoffroad.com/i-367062-...stall-kit.html