Gear ratio

That is true.

Manual trans have higher ratios. 3.42 or higher.

Autos have 2.46ish.

 

Depends if it’s a direct or over drive trans, I’d imagine it’s direct since those would be completely useless with an OD trans,

 

I have 308s in my 10 speed (od). I built it to get high mileage at high speed with light loads (engine is a 505 DD15)... I get somewhere north of 8mpg at 75 mph. Im averaging 7.5mpg over the last 40,000 miles counting idle time. A heavy load for me is about 15k.

 

Gear ratios have an effect on torque multiplication. I don't know if torque has any effect on a truck's ability to pull a hill (it definitely helps with startability though), but I do know that horsepower certainly makes a difference.

 

What is the engine and transmission in this truck? If it is a D13TC with a I shift 12 speed OD then this is a really good setup since the TC really likes the lower RPM's. Would grab this truck in a heart beat if pulling 80K or less.

 

This is a Volvo and if it has the D13TC (Turbo Compound) then the 2.46 with OD is a great fit. The TC loves the lower RPM's and can cruise in the 900 RPM range with full torque.