3.70 vs 3.90, what is the difference?

Both trucks will perform the same on a hill only time that 3.90 will be better than 3.70 is when you’re pulling over 80,000 on a 6% or greater grade the 3.90 might stay on the topside of the box while the 3.70 will need basement gears .

 

I would even venture into 4.10s, fuel mileage is not a concern heavy/off-road, getting moving without blowing the drive train is. Especially on tall 24s

 

Difference is 5.2% So with 3.70 at hundred mph at a given rpm the 3.90 at same rpm would be around 95. So if you are only going 50 at a given rpm with 3.70 the 3.90 at same rpm would be around 47-48mph.

 

Take the 3.90 then……

 

3.90 …

 

Did anyone consider engine torque ratings or transmission final drive ratios. I know he asks about identical set ups. Still more torque plays a lot into climbing a hill, without dropping gears. Since he’s on flat ground, I’d think the 3.70s would yield better fuel economy. If he’s got enough torque, power difference would be less noticeable. Technically the 3.70 would be faster top speed. And with enough torque faster from a dead stop, due to longer legs in each gear.

 

It really depends on what you plan on hauling if your going to be towing heavy loads then for a complete stop a 3.90 is going to have a good low gear to start off with, where as if your going to be hauling light loads you'd be better off with a 3.70.

 

Neither. I'd go with 4.10s if I were you. In fact, I'm getting ready to switch everything over to them myself and I run mostly paved state highways and interstates with occasional job site deliveries. 13 speed and tall 24s with a 925 CAT. 1600 RPM is 70 MPH.