I am new to the forum and have been reading how 4.10 or 4.56 gears will help get better MPG for my 4.7L. With that in mind I turned on the Tow/Haul for my trip home from work and saw a significant increase in my MPG. This was a short trip, approx 15 miles, withboth highway and town driving. I am going to continue to try this and see how it works over the long haul. Are there any negative effects to driving in Tow/Haul all of the time? Any other MPG tips would be appreciated as I love my truck but the pump is killing me!

 

I believe all the Tow/Haul mode does is change the shift points and possibly cut out the top gear. It's odd that it would help your fuel economy during normal driving, I would think the opposite... Maybe you were just driving more cautiously because you were paying attention?

 

It seemed odd to me too but I have read on here all day about going from the 3.55 gears to 4.10's or 4.56's helping milage. I am guessing that it gets the motor RPM's in a better spot in the powerband. I have read 2000-2300 is optimal. The tow haul on my 2005 locks out the last overdrive which essentially changes the final drive ratio at the transmission rather than the rearend. I was at about 2100 at 70 MPH. The drive was in Kansas City Rush hour traffic so it was less than ideal. Typically I am at 14.5-15 MPG, the trip home was 18.1. I am going to try it for a while and see, I just don't want to damage anything. Plus it takes alot of gas to pay for $1600 in gears.

 

don't trust the overhead display, always hand calculate your mileage. I keep track of mine on an excel sheet and make notes of what I did to the truck and when to see how it affects mileage.

 

if you push that same button 3 times it goes into fuel saver mode, and a fourth time will turn it into a hemi.

The tow haul or a lower gear like 4.10 or 4.56 helps in the city as its less strain to speed up, but on a trip on the highway it simply can't help. Think about a bicycle, its hard to start from a stand still in a higher gear and harder to keep a fast steady speed in a low gear.

 

RAMITONE, I understand your point but there is also a breaking point at which the motor simply does not have enough power for the higher ratios and requires more fuel to power it. Mine seems to labor in the final OD.

 

PYRO, I know the overhead display is only approximate but I am just using it to compare apples to apples. If it continues to look promising I will do the actual math.

 

I get best MPG at 75 to 80 on highway

 

It's possible to geta smidge better gas mileage in city driving by using the tow/haul for a lot of stop & go traffic. It has always been recommended to turn O/D off in vehicles so equipped when driving exclusively in the city. I guess this would amount to about the same thing.
I think you guys are completely missing the boat on the gears thing though. With the price of gas, I'm starting to see a lot of threads about re-gearing to 4.XX gears for better gas mileage. The gears ARE NOT an mpg mod, they are all about getting power to the ground more effectively and efficiently. Yes, most people notice a small increase in city driving, but you'd never make up the cost of the gears in gas savings. Even though they do nothing to increase engine power, they are still a POWER MOD, and should be looked at as such...

 

I agree that gears would be a power mod. but if a secondary benefit is better MPG with lower gear ratios it tells me that the engine is operatingin a more efficent portion of the power / torque curves. My drive is 75% interstate but in rush hour traffic there is alot of on / off throttle and brakes. I still showed 17.5 after the trip in this morning so I will let you know how it works out for the long term. This all may change with a few mods that increase HP and Torque. Right now I am looking at a Gibson exhaust either the single or double side exit and possibly the spectra CAI. Any thoughts?