how do you compare going to a bigger tire (say a 33 inch compared to my 235/75/15 or whatever it is) and swapping to a higher (numerically) gear vs my speedometer? Will the gears compensate the larger tire size and will it keep my speed the same or will it cause a higher RPM? right now at 70mph im around 3k on the tach.

sorry for the newb question but thankfully we have this section of the forum!

 

what engine do you have? It sounds like you have a 4banger. If you regear to bigger tires it will keep your tire to gear ratio near stock so you won't be off by much, and if you undergear it you will get higher rpms.

For 33's if your a 4banger 5speed i would run 4.88s

 

sorry, i have a 22re and 5spd.

i am new to trucks as well, so do you have to regear the front differential as well?

 

If you ever plan to use 4WD, then yes, front ratio must equal rear ratio assuming you have the same size tires on both ends.

And for general information, see:
- http://www.4crawler.com/4x4/4R_TechI...tml#DiffRatios
- http://www.4crawler.com/4x4/4LoCalc.shtml

 

Generally, it works out to one size bigger tire = 1 size lower (higher numerically) gear ratio.

For manual tranny:
31 = 4.56 (stock)
33 = 4.88
35 = 5.29
37+= 5.71

For automatic tranny:
31 = 4.88 (stock)
33 = 5.29
35+=5.71
Personally, I feel the automatics are undergeared stock, so I would go one step lower, especially if you drive on the highway and need overdrive.