change rear end ratio or change transmission

You will not like any lower gear than a 3.55 ... maybe a 3.42 If I can find the hp/torque curve for an emodel I will post it

One of my buddies went from a 3.70 to a 3.36 on his 6nz to run lower rpm out west. The combination of lower RPM making less HP/Torque lost him almost a mile per gallon vs keeping the motor spun up.

 

Did he try running a gear lower to bring the rpms back up? The theory of those 2.80 or 2:90 whatever ratios is to run the transmission in direct and have less parasitic (no sure if that's the right word) loss.

 

I appreciate all the comments, ive located a set of DS404 336 rears im going to throw in and give a try. im getting both diffs for little of nothing cost wise. i figure ill try just running in 16 or 17 most of the time unless i get out in the flat lands and can crank her up and run in the high hole. i guess iff i dont like it i can always throw my 370s back in her.

 

What are all the ratios? Like is each ratio a certain distance from each other or are they just kinda random? I’m 22 I’m looking to buy a truck this year and want to make sure I’m not in this situation haha. My company truck right now is a 379 with a c13 to a single turbo with 3.55 and 13 speed and its running about 1550 at 70. I never run it higher or faster unless I’m passing someone cause it just sounds like it’s working so hard. How high is the highest rpm you should be cruising at?

 

Doesn't hurt anything to run higher rpms. You could run at 2000 all day long. Just hurts the fuel mileage