I've owned nine Ram 3/4 ton and 1 ton diesel pickups in the last eight years. I put 35k-45k on per year with a mix of heavy towing and daily driving. I've ran the Nitto AT G2s, Toyo AT2s, Toyo MTs, Cooper Discoverer AT3s, Hankook ATMs, and Cooper Discoverer STTs on each one. From that list here is my ranking on each:
#1 Cooper Discoverer AT3 - only tire I've ordered multiple sets of and will run them on any vehicle I own now for an AT tire. They have excellent traction on dry roads, wet roads, ice and snow, muddy woods and fields, and gravel roads. Best AT tires I've had in mud, they keep pulling like an MT almost. They also wear very well, even when not rotated regularly. The last set I had, 315/70/17s D rated on an '05 3500 SRW Ram work truck. Regularly pulled heavy every weekend. Rotated the tires every 15-20k-ish miles and they've lasted 8 years and ~70k miles and still have 4/32 tread left worn evenly and still have them on. I also have a set on my 14 Ram 2500, 12-15k miles on them and only wore down 1/32, 95% tread left. What I like about them besides lasting long and having great traction is the traction never changed as the tire wore, even now with barely tread left they still have good traction. Just put a set on my wife's Jeep and my dually. The only negative thing about this tire is the sidewall looks like a passenger tire, has an aggressive tread but smooth sidewall and doesn't have that "tough" look.
#2 Cooper Discoverer STT (now STT pro)- Owned one set, size 35x12.5x20 E rated, on a '12 Ram 2500. Put 30k miles on them pulling an enclosed trailer from MN to WY, loaded with a sled deck, or daily driving on highways. Rotated every 5-6k miles regularly and wore even. Great dry, wet, gravel, and snow traction. Really good ice and mud traction, very surprised how well they did on icey WY roads in the wind. After 30k miles they still had 40-50% tread left. I would buy another set in a heartbeat, but for the driving I do an AT is better for me. Negatives= price, they aren't cheap if you have big wheels or want big tires.
#3 Nitto Terra Grappler G2s - Owned one set, on a '12 Ram 3500 DRW, size 285/75/17 E rated. Put 30-35k miles on, rotated every 10-15k miles. Still have four tires with 35-40% tread wore evenly, two are at 20% wore uneven due to being a dually and the rotation the back insides wore like sh*t. They are showing some weather checking in the tread from the pickup not being driven regularly I think. Good traction on dry, wet, and gravel roads. Pretty good ice and snow traction. Did surprisingly well in muddy fields and woods but not great. I'd buy another set, but based on price and performance vs. the Coopers, I ordered the Coopers.
#4 - Hankook DynaPro ATM - One set of 295/70/17 E rated on '10 Ram 2500. Had 30k miles on them when I sold the pickup, still had 50% tread. Good dry, gravel, ice and snow traction. OK wet road traction, I could get them to slip easily under a heavy throttle. Muddy woods and fields were OK but you better have 4x4 and a way out, obviously not a mud tire but did not perform like the Nittos or Coopers. I liked the tire, they wore even and lasted a long time, but for the traction they had/didn't have I'd consider others over this tire for my heavy diesel. Would be better suited for a lighter gas vehicle or SUV, I'd buy them for a Jeep or 1500 pickup.
#5 - Toyo Open Country MTs - One set 35x12.5x17 E rated on 08 Ram 2500. 25k miles put on and 50% left. Great traction on dry, wet, gravel roads and mud. Surprisingly great traction in ice and snow, could back up in 2wd on an icey hill without slipping. Wore quickly with a heavy load on, could notice a difference in tread depth from front to back after trips out west, but after rotating they evened out. I would defiantly buy them again, but they are way more expensive than the other tires in my size.
#6 - Toyo Open Country AT2s - One set of 285/70/17s on a 13 Ram 2500, pulling heavy regularly. Have 20-25k miles on them now and are down to 40% tread. When they were new the traction was great in all conditions except muddy woods and fields, they gummed up and wouldn't clean out. As they wore, the traction decreased exponentially and now with 40% tread I'm debating taking them off before the snow flies this year. I won't buy another set especially for how much they cost compared to other brands.
