Hey guys I have 07 4door lbz, I pulled my first trailer with it, an 8500 lb toy hauler, I noticed that when I was using the tow haul mode the engine was braking while coming down the hill, I noticed slowing down and the engine seemed to make a noise like I was in a lower gear, is this normal? I think it is but I am new to the gm scene. My rig has 8000 mi, and I noticed a similiar noise while pulling some steep grades any help is appreciated. Everything is stalk except, 305x75x20 tires, my mileage was also 8.0-9.5mpg. is this normal with this weight, keep in mind I was pulling a lot of hills but on the flats i got no better than 10 mpg

Grade braking is a standard feature of the Allison and is completely normal.

What mods if any are you running?

I assume that you have corrected your speedo for tire size? If not, it's tough to hand calculate fule consumption. The DIC is worthless.

no mods yet what is the safest way to add hp and fuel mileage. when it comes to tuners i am confused on what is the best for the duramax I seem to get conflicting reports what is the safest. how do you adjust the speedo for tire size

hello my truck is an 06 lbz straight piped ,superchip with tire size correction and speddo calibration and the mileage has sucked for 25231 miles!!! pulling 18 foot haulmark enclosed trailer approx 5000lbs to casper wyoming last weekend 9.5 to10.2 at75 mph dropped to70 no difference just come to except the facts. oh by the way my tires are 295 75 16 nittos and the superchip has been installed since the odo was 5000 mi.

I agee, you need to take into account your tire size(correct it to get accurage mpg). These trucks eem to be hit or miss on fuel milage, mine stock gets 14mpg that my old 96 doing the same thing (w'/a 4.10 rear and 4spd) got. Grandte dthe new truck does have more power but still. FIrst thing to do would be drive it easy, put an exhaust on it, and a slgiht slight programmer.