If you have a 3.73 gear now, a 4.56 gear w/38's will achieve roughly the same RPM per MPH as stock.

If you have a 4.10 gear now, a 5.13 gear w/38's will achieve roughly the same RPM per MPH as stock.

A 4.88 gear w/38's will yield roughly the same RPM per MPH as a 3.96 gear ratio on stock tires, and is probably the best combination of pulling and economy. Of course, economy is a relative term as the mass of the rotating assembly is about to be triple or more. Certainly not good for stop & go driving. :)

Hi Bill
so you recommend 4.56 if i want the same as stock`s performance with 38`s, but i didn`t understand the 4.88 very clear , can u explain it more please thanx

Bill was stating that eventhough 4.56 is optimum on paper the 4.88 will help get the bigger tires moving better in the real world abd also will help whenever you pull a trailer.

Thanx for getting it clear for me !
thanx to all