Gears = mpg???
 

I'm running a 99 Drw and getting about 14.5 mpgs with 355 gears. I have two buddies that have the same truck running 410's and they get 20 mpgs. I find it hard to believe. Yeah it takes more to get mine going but is it really that big of a difference? Should I swap to 373's.? What is the best setup for this truck?

MPG also has a lot to do with driving habits, gear ratios, tire size, transmission and many other things. I had a 01 6spd speed with 3.55's and my buddy had an 01 Auto with 4.10's. Bone stock he usually got 1-2 mpg better than I did. But I am also 32 yrs old and he is 57 yrs old. Our driving habits are totally different.

Now if you do much towing you will like 4.10's or a higher gear ratio.

What size tires is on the truck? 3.55 gears you should get better then the 4.10s. Bigger tires will change the MPGs. You have the smarty is the tire size correct?

My driving habits=:popo:

Gears = mpg???
 

If you are doing a lot of in town driving don't look for much more. I was avg around 16-17 in town with my 3.55s however when you get them out on long runs that's where the high gearing helps. I could see any where up to 21mpg just depending on driving habits when I went on long trips

Tire size = 235. yeah I adjusted the speedo with the smarty. It is just weird. I don't drive with a lead foot.

Environment Would be My Guess
 

Are you talking straight highway long-distance, mixed, start-stop around town? Being more mixed mode leaning to start/stop would explain it. Taller gears only translate to better mpg on the highway, all else being equal. Higher gears means worse fuel mileage in urban environments with a lot of start-stop driving.

it also depends on if they are trusting the overhead or hand calculated. I will take my 3.55's any day over 4.10's

Gears = mpg???
 

I liked mine for running down the road empty but my355s killed me towing and in town. It's also a pia for trying to idle around pastures check fences and stuff.

Also it is possible for a truck with 4.10s to get 20plus my old roommate had a 01 3500 that got around 20 mpgs hand calu. on a regular basis

If I had 4.10's I would want a pretty tall overdrive ratio, maybe even a gear vendors.

I do about 60% city and 40% highway

I have 3.55's, in town I get 15-16mpg empty, but on the freeway Im breaking 22mpg empty. I wish my town driving was better, but realistically, its 4mpg better than my 1/2ton gas rig ever got! So Im happy

Diesel Trucks are Great on the Highway
 

I run bigger than stock tires on both trucks. 3.73s in the '07 and 4.10s with a Gear Vendor in the '91. So both my trucks are geared for the highway because that's where most of my driving is. If it wasn't, I'd be driving something else.

Id like to have a Gear Vendors just for the fun of it, but theyre slightly expensive

I have 3.55 on a 2wd and am getting a little over 19mpg around town, haven't had it on a road trip yet, so don't know highway mileage. Tires are 245 75 16, considering 265 75 16 next time I need them. Is yours running smoothly? Is the air cleaner good? Dragging a brake?

i can get better mpgs out of 3.55 than 4.10 with a empty truck. heavy towing and tire size will play into mpg too.

i'm running 305s, with 3.55 gearing, roughly 50/50 split between highway and city driving, 150 hp sticks and a tst box, I'm averaging right around 19.3 currently, hand calculated, not corrected for tire size.

Thats not bad at all dukeboy. Found a set of 3.27's to replace my 3.55's, Im shooting for 30mpg highway :yeah:

I wish I hat 3.73's for around town, I get poor mileage unless Im going over 50.. The constant getting up to speed is killing me with these 3.55's