I have a 2000 ford ranger 3.0. It has manual hubs which are fairly new. I was driving down the expressway and I got this crazy vibration. I switched it to 4 wheel drive and it went away then came back. Got it home and locked the hubs took it for a drive it happened once so I switched it to 4wd then back to 2wd and it hasn’t happened since with the hubs locked.