I had planned on purchasing a mega cab with 3.73 rear gears after looking one over. I found out today that it was sold and the only other one left without going to the 6.7 has 4.10 rears. I usually run the highway between 70-75 mph. What should I expect fuel mileage wise? It has the 48re tranny.

 

I have a Megacab w/ 3.73 gears. Here are a few things to consider. How do you use your truck. If you plan on installing larger wheels and tires you may want the 4.10 gears if you tow. I put H2 wheels/tires on and it is now geared too tall for towing (w/ my 3.73 gears). When I tow on long trips I switch back to my stock wheels. If I had 4.10 gears I would be OK with the H2 setup when towing.

On the other hand, if you don't tow alot the taller gearing(3.73) is the way to go. With stock wheels I turn 2000rpm at 70. With the H2's I turn 1750 at 70. I like my truck better w/ the H2's on it and in hindsight I would have gone with 4.10 gears.

To address your question on fuel mileage, I again say it depends on how much you tow. I think you'll get better mileage towing with 4.10 gears. If you use a truck for daily driving the 3.73 will be better. With my stock tires I got about 16mpg at 70-75mph.

Bob

 

I would buy it the 6.7 get crap for mileage for the price difference you could change out the gears and then some better get it before I do

 

The 4.10 should give about 10% less fuel mileage than the 3.73 at hwy speeds. The 3.73 will run about 1900 RPM at 70 mph while the 4.10 will move up to 2100 - 2200 range. This is why the MPG goes down. You can compensate for this by going to 10% larger tires than stock. You will have to adjust the ECM programming for the larger tires to get the speedo to work correctly.

 

With my 35" toyo mts, I wish I had 4.10 gears.

 

It must have the new six speed auto. the 48RE did not come with the 6.7

 

Yep if you get 4.10's just get 35's on there and you will love it!!

 

Thanks for the replies, I really don't want large tires. I had 40 inch groundhawks on a blazer when I was young and those days are over.

I'm trying to stay away from the 6.7

Thanks

 

Buy the truck, we can swap gears

My mileage sucks with 3.73's. A run to LA and back netted me 15mpg down, 13mpg back. 70-80mph the whole way both ways. Lifetime avg. on truck since new (8500 miles) is 14.1 hand-calculated.

I can't wait to see what happens when I mount my 35" MT's...

 

Wowwww.....my 6.7L & 68RFE will do that good, or better, at 9k miles.

Nice to see there's some "honest" 5.9L guys reporting crap mileage from their trucks.

 

It is not the 5.9 causing the poor mileage... It is going 70-80 that affects the mileage.. If JCleary tried keeping rpm under 2000 from the startup and limited max highway to 65 MPG would go up.

I can make my mileage go down to 15 if I drive it hard. If I drive it like I normally do I get 17mpg avg (50% highway and 50% around town). Don't blame the 5.9 as it is the driver that is USUALLY the cause of poor mileage.

 

yeah my mileage goes from 14 at 65 down to 8.9 at 105,can't figure out why?

 

Your truck isn't even CLOSE to being broke in and getting mileage yet!!!

I gained 2 mpg just by rolling past 20,000 miles

If I gain 2mpg every 20,000 miles, by the time I hit 200,000 miles, I'll have a 40 mpg truck!

 

I got 17.2 on a trip from CN to NJ then to MD going about 70-75 half of the way and then 65 - 60 the rest. At 55 it gets great mileage but that's too slow. At 70 mileage isn't too bad but with 3.73's it would be better. I consistently have been getting 15.2 for the last couple weeks in 60 city/40 hwy driving. My average mpg for last year was 15.x.

 

Dam if I will drive like a grandpa just to say i am getting 17mpg