I'm trying to decide on some gears for my 4.8/4l60e truck I want to know how many rpm's I'll be doing roughly at 70 mph. thanks for the help.

 

well i run 4.10's with a 29.75(stock) tall tire and i run 2400rpms at 70. that should be a good starting point for you

 

Ive been wondering this also. I still cannot decide between 3.73's and 3.90's.

 

I personally would go with either 3.90's or 4.10's. The cruise rpm difference between either of the three is not going to differ more than 150-250 rpm's at 70. 3.90's or 4.10's will give you more grunt down low though.

 

About 2260rpm at 70mph with 3.90 gears and a 4L60E.

 

Yeah I think I'm sold on the 3.90's, my dad has a similar truck but extended cab, and what a night and day difference over the 3.42's.

 

Im also in that dilema of changin gears, not sure if either getting 3.73's or 3.90's. but these 3.42's really suk

 

I went from 3:42's to 3:90's and I very happy. I have 275/60/17's and I turn right at 2500 at 80 MPH. It is not really turning very high at all. Last time I took the truck on a trip, I went 70-80 MPH for about 300 miles, and got 19 MPG. I am very pleased, the only thing about 3:90's is it is not a factory option on these trucks, so if you don't have a custom tune your speedo will not be correct. I have a hypertech and it is set at 3:73 gear ratio and it is about 5 MPH fast. Set at 3:42 I think it was 10 MPH.

 

last trip i took home to louisiana i was getting 20mpg with my 4.10's and my stock tires. that calculates to 500 miles to a tank

 

oh i forgot, that's with the cruise set at 70 turning 2400rpms with two people and about 300lbs in the bed