TurningOfTheWheel wrote: ↑Sun Oct 03, 2021 12:12 amI've read of 'modern' trucks / wheel sets where each axle can 'steer' separately from the other. Though I don't know if it's heavily used. And from what I've seen and what you are saying, the wheels on a given axle are solidly attached to the axle so that the 2 wheels and axle normally spin as one. I'm wondering if that's just to save money or if there is another reason.photobug56 wrote: ↑Fri Oct 01, 2021 11:46 pm What is truck hunting, and what can cause it?The Wiki article on hunting oscillation has a useful animation to see what's going on. I can't explain the phenomenon very well, but as I understand it, at high enough speeds, slippage can occur and the two wheels on each axle can start spinning at different speeds. When this happens, there is an oscillation induced in the vertical axis—from a bird's-eye view, the axle will appear to turn back and forth. It's called a "hunting oscillation" because the wheels are "hunting" for some equilibrium where they are either both spinning at the same rate or agree on the direction they should be headed given the difference in their rotational speeds.