10 speed 3.58 ratio or 10 speed 3.70 ratio

Should be the same depending on driver habits. Obviously you might get about the same mpg's out of the 3:58 truck going a couple or 3 mph faster than the truck with 3:70's. But not necessarily. 10 speed doesnt mean much. Are they direct or overdrive transmissions? Guessing the 3:70 truck is OD for sure and likely the 3:58 one as well. Regardless, I still think it is up to the driver.

 

you have to consider your desired speed and weight also. heavier loads with more stop and go the 3.73 might be best, more interstate the 3.58 may be better etc etc. it's just not that easy.

although chances are that egr detroit mpg will suck regaurdless. also the early 05's had the old style egr system which they don't make parts for. make sure it has the newer system because if the old system fails it's $5k to upgrade to the newer one

 

diferent 10 speeds can have different final OD ratios.

Pulling lots of weight in the hills, the 3.70 might keep you from downshifting as much and give you better mpg.

Running light where it is flat the 3.58 would.

 

01-06 and some 07 have just EGR, 07 and newer have EGR and DPF, 10 and newer EGR DPF and DEF.

Yes a 13 would be better as you would not need to drop as much in gearing to maintain speed on hills.

 

and of course you need to check what the ratios are on the 13 speed, they make different final drive OD ratios, and a double OD.

 

johnnycage.....

There are so many variables involved when choosing the right truck for your needs, that the only way to be sure that you're making the right choice, is to be VERY specific about how a given truck is set-up and HOW you will be driving it. Knowing your cruising speed is a very important thing to know when choosing a truck.


For example........

At a cruising speed of 65 mph..... If you were to choose the truck with the 13 spd and 3.55 ratio and ASSUMING that the drive tires are NEW bridgestone M720 lo-pro 22.5's......THEN..... At 65 mph you would be mathematically turning 1,437.4 rpm's ( the rpm's would be a little higher with used/worn M720's).

Different makes and models of lo-pro 22.5's, have different diameters..... You have to know what they are, to accurately compute rpm's at a given mph.

A very important number to know about a tire is its RPM...... Not rpm's in terms of revolutions per minute, but in terms of revolutions per "MILE" !!!!!! In other words, how many times a tire turns one complete revolution over the coarse of ONE MILE. For the M720 lo-pro 22.5, that number is "512".

If the 13 spd is an Eaton, ( which it almost assuredly is ) then the top overdrive gear ratio for that transmission is (.73).

Hope this helps.