kpgncc444

Hey guys I've done a lot of research here lately and the more I dig the further undecided I become. Hoping someone here has some real world experience with what I will be doing. I'm looking to do a gear change. I'm trying to decide between 4.11 and 4.56 gears. Heres the background: I have a 13 Kingranch. I've owned it for 2 years now and have 80k miles on it. So as you see I drive it A LOT. On top of that at least 40k of those miles have been towing. I race ATVs nationally and I'm usually pulling 1000 mile round trips every other weekend through 3/4 of the year. Bought a new trailer at the beginning of the year as we needed some more room and this thing is a parachute! It's an 8.5 wide x 16 long HD built with 7 ft ceiling. Needless to say this pulls way harder than my old 6x12 enclosed. I'm usually hauling 4 quads, tools, gear, etc. Usually turns out to be about 5000-6000 lb trailer and all and a little more on a few occasions. Biggest factor is wind resistance more than weight though. Tire wise I've upgraded from stock 275/55/r20 to nitto exo grapplers 275/65/r20. Their website calls it a 34in. tire but real world mine measures 33.25 at the pressure I run. I currently have 3.55 gears and and this new trailer really sucked the life out of it. Obviously 6th is not useable, but only on flat ground can I use 5th and at the first sight of incline I've got to drop to 4th. I'm not concerned too much with mpg loaded as I'm always in a hurry I don't expect great mileage anyway. But I would like to get a little back empty. I run interstate between 70 and 80mph empty or towing. With my towing frequency and higher interstate speeds everything seems to point to wanting the 4.56, but when I am unloaded I'm still doing a lot of hwy driving and concerned that cruising 80 empty turning 2500 rpms (what I calculated) might be too much. Would the 4.11s be enough?

Honestly after reconsidering my driving history I probably needed a F250 instead, but I just love my little ecoboost too much! Any real world info to share?

agetech

I have a 20' x 8.5' enclosed car hauler that I tow behind my eco loaded with a 1972 GTO. I've got 3:31 gears and the truck pulls great. But I have also pulled my buddies 14' enclosed motorcycle trailer and I think his trailer pulls hard. I get 9.5 mpg with my trailer loaded and 11 mpg pulling his.

QwkTrip

Have you considered trying a tow tune first? Gears are a lot of money and effort.

mechanicboy

6th gear is 0.69 and 5th is 0.86 This means that there's a 24% increase in rpms when downshifting. Going from 3.55 to 4.11 will result in a 15% increase in rpms and going to 4.56 will result in a 28% increase in rpms. If you have lost 6th gear with the new trailer and 5th barely holds it them 4.56 gears might be for you. Unloading the turbos might increase towing MPG too.

Another thing to consider is maybe you need a tuneup to help increase power. Replace your spark plugs and make sure they are gapped per recommendations on this site. When towing you should run premium, says so in the manual and will give you a small bump in power/fuel economy while towing. Make sure you air filter is clean and check your intercooler/radiator for debris.

You could also get a tuner to help with power, but make sure you tell them how heavy you tow so they make a safe tune for you.

kpgncc444

I have already went with a tuner. I currently use the Livernois tuner and only use the 93 octane maps for tow or performance. I've thought really hard and know the 4.56 would be great, but how bad is that going to hurt empty mileage when I'm cruising interstates at 2500 rpms? But yes, 6th is completely useless and if you don't put the gear select in manual it tends to keep it in 4th almost all the time so 5th isn't much.

acadianbob

Kenferg1

He's running into physics. Horsepower required be proportional to the square of the surface area. 4.56 would give terrific mechanical advantage though.

QwkTrip

Power required to overcome air drag is proportional the Area, not the square of Area. Speed is the killer as the power needed increases by the cube of velocity.

Kenferg1

I knew it was something like that, thanks for the bailout.

QwkTrip