I have no problem with my stock gearing and OEM size KO2 tires at 13,000 feet.

I went with 285/70 E load, not stock size. I have no problem with the 285/70 E load KO2's I have currently at altitude but wanted AT4W's as I find the KO2's disappointing in water and real sketchy in winter <50% tread. I also statically have ~600lbs extra on my rig before putting on the RTT and loading any gear. Even with my supercharger and custom tune I still definitely feel it when driving through the mountains trying to maintain 80mph.

I’m curious if you ever considered the Baja Boss AT’s or a 34 x 10.5 size tire?
Weren’t the E load AT4’s less in weight? Anyway, I hope these AT4’s perform well for you. I think staying with a 285/70 was a good decision.

funny timing on this comment. we just got back from our trip to Durango Co area. 14mpg from phx to Heber AZ. from there is was 18mpg to Durango. 34x10.5's C rated. Power felt fine actually. it wasnt as bad as i was expecting, usually we take the ford with the 6.7 powerjoke.

we had lots of snow, slush, and rain. the toyo at3's were fantastic. there is a tricky hill up to the cabin and i did it in 2wd one of the times with lots of chatter from the ABS lol. otherwise 4x4 and momentum was required due to snow/ice.

I frequently go camping with some friends and drive through the mountains to go to Western/NW CO, southern NM or Western UT. I live between Denver and CO Springs. Typically when going up through Vail or going South to NM is where I feel the power hit as well as have heat issues with the brakes. Right now I get 15-16mpg on flat areas and 13-15 when going through the mountains.

Going from AZ to Durango, CO you still haven't gotten to the mountainous areas of CO yet so you probably didn't feel it as much. Durango is at 6500 ft; I also live at 6500 ft so That would be typically be my starting elevation before climbing through the mountains. Once you get >9000 you can really feel it a lot more.

Before the SC sometimes I would have the pedal to the floor to climb I70 through the mountains at freeway speed. With the SC it now feels comfortable to drive and doesn't downshift as much so I am not staying at 4k rpm's on the climb.

I did look at Baja Boss AT's as well but they were just as heavy if not heavier.

As for 34x10.5 they are only made by toyo(which are not rated as well as AT3/4's) and BFG KO2's(which I am getting rid of). I had bad experiences with toyo car tires before so I don't really like them, and the KO2's I have are at 6/32's now and are horrible in rain and dangerous in snow.

I have dedicated hakkappelita LT3 studded snows for winter but occasionally have early/late snow and hailstorms I had driven through when not on winter tires.

The E load AT4's are heavier than the AT3's and the C load AT4's funny enough are the exact same weight as the E loads.

I absolutely love my General AT/X tires, i had 2 sets of BFG TA K/O and while they looked good and rode good and wore out like a normal tire, i had to keep them balanced every 15,000-20,000 miles to keep them smooth. I recall getting about 40,000-50,000 miles out of them. A friend mentioned to me to try the General AT2 back in 2014 so i bought a set for my Ram dually. FOOKIN'AYE best tire i had ever owned by far. I instantly ditched a set of "decent" 285/55-20 off my Limited 4runner and put the 305/50-20 Generals on it. Not much long after i got another set of the 305/50-20 for my Tacoma. When i sold my dually and got a ram 2500 in May 2017 i put General AT/X on it day 1. My 2008 4unnner i bought used in 2019 got a set of General AT/X on it as soon as i could put them on. <-- they are still on the 4runner today with 97,000 miles on them and i will bet you i am going to get 120,000 miles out of them. I have crossed the worst ice storms this country has to offer towing trailers, pulling hills, sleet, snow, rain, and heat that melts your tires into the pavement, and the General AT2 and AT/X are by far the best thing i have ever driven on. They wear like iron, have traction i have never experienced before, and are nothing like any other tires i have ever owned. I just balanced and rotated my Generals on my 2008 4runner about two months ago for the second time. I took them off, took them to the tire shop for their second re-balance, and rotated them at 90,000 miles. The first rotate and rebalance was at 40,000 miles, most folks are replacing tires, i was doing my first balance and rotate.
Both of my ram diesels got about 60,000-70,000 miles out of them, both of these were dedicated pull trucks and towed a heavy trailer. My wifes previous 4runner and my tacoma, we both sold them prior to wearing the tires out so i cant tell you how many those sets got but i remember seeing my tacoma running around town for about 6-7 more years with the tires it had on it when i sold it. They have crazy traction in the ice and snow and sleet, the lugs "bite" well and pack the snow and sleet into the tread so it doesnt bury you down. They are designed a lot like the BFG but the sipes in the tread are a huge benefit to the traction. Also they are studdable, the holes are cast into the treads. Whats crazy is how soft the tire feels, your first 500-1000 miles you will swear they are as soft as chewed bubblegum and you will swear they are going to wear out like a drag slick, but somehow the rubber keeps on lasting. The rear dually tires pictured had never been rotated, and had a trailer hooked up that trucks entire life, and they had about 40,000 miles on them in this picture. I can guarantee you that you wont regret trying these tires out.

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Appreciate the input but I am guessing you may have misinterpreted, as I ordered falken wildpeak AT4W's, not General Grabbers lol.

I don't daily the 4runner but got about 40k out of the BFG's till they got sketchy, but tires should be changed out after 7 years anyway due to rubber aging.