[v10sport]

I was considering going with 5:13's but I think I want more gear. Im really pondering 5:38's

Here is how it breaks down

5:13 at 70MPH - 5:38 At 70 MPH

42" tire 1982 - RPM 42" tire 2078 RPM
40" 2081 RPM - 40" 2182 RPM
37" 2250 RPM - 37" 2359 RPM

Also if I do run a 42" tire, even with 5"38's it will not bring me back to the factory ratio with 31's. My truck had 4:10's and with 42's and 5.38 its a 4.05 ratio

 

[B.A.R.K]

So what is your question?

 

[demonranger]

Either one will work fairly well. you had a fairly high (numerically) ratio from the factory which will give you more low end but sucks gas @ high rpm. most likely you have a towing package that gave you this ratio. look @ the factory available ratios and attempt to stay within that range rather than going back to exacly what you had. The choice of gear ratio depends on what you want to do with the truck

i.e. off road only, on road, city driving hwy driving, towing, hauling, wight of trailer/load and when you get off road what are you going to be doing mud, rocks, trails, etc.

If you want to go with the lower gears (higher number) it will be better for towing, crawling, city driving the taller (lower number) will be better for mud, hwy driving, light truck duty.

 

[v10sport]

Fuel mileage isnt a concern since I drive this about 6K a year. After looking for gears, I see after 5.13, there is no available gears until 5.89 for the Dana 70 and Im not finging any reverse rotation Dana 60 gears in that size either.