10-Speed Peterbilt 379 - Save Fuel with 13-Speed Upgrade?

O ok so we are on the same page here.

 

Yeah, its just that studies have shown the direct drive trans are better for fuel mileage. But they don't take into consideration the different types of freight and freight lanes.

 

Go figure thats not a surprise, office workers telling the drivers what works best no exceptions....

 

I am new here and just got back into trucking a year and a half ago since 99
I have driven many different trucks I used to like the 15 spd od alot and I hated the 13 and 18 but last year when I got my fld classic with 500 detriot with 13spd 3.58 lp 24.5 It would pull well with some cats until it got to a steep hill. Now I have a 379 with C-15 10spd 370 rears and 11r24.5 rubber.
It pulls ok up to 1500 but to me is week because its the mbn(bridge) engine
and I really miss my 13spd trans. When I get the chance to get a 6nz ecm and a few other changes I want to find a 13. But my question is what difference in final ratio on 10spd vs 13. I always felt if my classic had 370 ratio with tall rubber would be perfect because it would easily get into triple digits bobtail if I wanted but my concern is to make my 379 pete last me a while. Any opinions would be great

 

Just remember you a wanna be and Ive driven 1.5+ million miles and can get 1 to 2 tenths better fuel mileage with a 13 or 18 speed in a local or regional run shifting up and down through the gears several times a day. On a long haul situation the extra rotating mass in the 13s and 18s is so minimal it probably couldn't even be measured in hundredths of a gallon.

 

A 10 over has a .74 and the 13 has .73. Almost exactly the same. Only 1 100th of a turn.

 

I take it that you understand where im comming from.

 

No I was laughing at the wannabe part...

The driver is the determining factor in fuel mileage. Regardless of what trans or rears they have.

 

The driver is only part of the determining factor of fuel milage. A properly spected truck has just as much to do with it. I do agree that a driver driving properly can get better fuel milage than a driver with a heavy right foot winding it tight through every gear and running faster and harder than need be can be hard on fuel. How ever a truck geared to low or to high for the type of freight and road conditions or under powered for the load it pulls will effect fuel milage more than any driver ever could.