Have you ever wondered what "DIFF LOCK" in Spintires is all about?
The "Diff" part of that functionality is explained in great detail in this video: Around The Corner (1937) How Differential Steering Works (it is basically an advertisment, but it will be one of the most informative ads you'll ever see).
Figuring out what the "Lock" part means is left as an exercise to the watcher...
also properly done logging truck mods, with proper capabilities, no overpovered stuff TY
I have no recommendation for a map, but for a vehicle mod: My all-terrain variant of the C-65115 utilizes off-road wheels and allows to use the log carrier with crane as well as the log crane carriage. For a real challenge, you can use the medium log trailer with this mod, too.
All these mods just add more attachments without changing the vehicles' original engine stats.
no maps tho
I haven't played many map mods yet, but I liked River Tura quite well. Although it probably doesn't meet your criteria of hard, challenging maps with hour-long log rides. However, it is a nicely done map and the area with all its log stations does pose some challenge when doing several log rides in one session, because the trails leading to and from it wear out pretty heavily.
EDIT: Just remembered that there's another map that could be more up your alley: Map Three Rivers. It only has one log station and one lumber mill, but I didn't finish that one because it was too hard for my taste.