1st reports on the new 2015 GM p/u's

Dadoffourgirls wrote:
Jim - In 2014, GM made the 4.10 axle standard. There was information that the 4.10 improved fuel economy over the 3.73 up to 60 mph. If all your driving is over 60, it was not going to be improved. If the majority of time you are under 60, it was better.

Michael:

As a former 3:73 owner, and now a 4:10 owner, it's a little puzzling to see the 4:10 getting better mileage than the 3:73 with all else equal (including the new trans) -- the math makes no sense. But I can say for sure that this 2015 6.0L w/4:10 gets very similar mpg as did my 2003 6.0L w/3:73 when hauling the same TC. But, 4:10 gets better mpg empty than the 3:73 -- between one and two mpg better.

But it still makes me wonder if the 2015 6.0L and the 6sp with 3:73 would also gain in mpg for the same reasons the 4:10 does. If given a choice, I'd still like to try out the 3:73 under the same driving conditions and with the same drive train (except the RE) and see what it gets.

I'm real happy with this truck, but would really like to have that option (3:73) because I don't tow nearly has heavy as most do, and would surely gain with that RE option (I'd think so anyway) and without losing that potential for better mpg.

I know, I know, who cares about mpg with a 2500HD, which we buy to do the work not to save $$$ on gas -- but still, all things being equal, if I could get the same truck (basically) and gain one or two mpg better (10%), then why not buy it. I would, for sure -- but am probably among a limited number of 2500HD drivers because most buy it for towing, not hauling a truck camper at 3200 lbs.