Best gear ratio for my truck

My gear ratio is 3.58 and i got some 265/75/r16 on my truck. I originally had 215/70/r15 some say would pull my mpg back up if i were to adjust the gear ratio. What gear ration would be best for my truck?

 

Which can make it further offroad. 4wd open or 2wd locked?

 

4wd open by far!! I'll see if I can dig up a video (I think ARB made it) that shows 2wd locked vs 4x4 open.

As for gears, well 4.10 or 4.30 would be a good ratio if you plan for just on just on road driving. If you want more pep you could go with 4.56's or 4.88's. That's a big step up but since you are an auto it shouldn't get your 75mph rpm's too high.

 

Thanks does it really make you gain mpg? And im mostly on the highway

 

I think it helps more with manuals since the torque converters helps autos out a lot during takeoff, but on the freeway, my V6 with 33" tires didn't like to stay in overdrive because it didn't have the power at 1900rpm to turn those heavier tires that fast. Once I regeared it never downshifts on the freeway but I went for overkill and got 4.88's and run at about 2700rpm on the freeway now. Because I went for overkill I lost a little fuel economy but it wasn't more than 1 mpg.

 

I was wrong it was made by 4x4TV. Here's that video.

https://www.youtube.com/watch?v=yMLHtApOCwc


Anybody know if the 2nd gen 4spd auto is the A340E/F? I can't find anything to comfirm that... Trying to figure out what ratio the overdrive is on his tranny.

EDIT: Assuming you have the A340F, your OD is 0.705:1 and your factory rpm at 75mph should have been about 2400rpm. If you got to 4.10's with the 265/75R16's you should run about 2350rpm and with 4.30's you will run about 2450rpm so you are almost split down the middle there. 4.56's would get you up to about 2600rpm.