everytime i accelerate as soon as i start moving there is a slip or jerking kind of feeling. I was told this could be either u joints or i have to grease the slip yoke on the drive axle....not too sure on how to do either of those so any help/advice would be appreciated. Also, whenever i flick the switch in my dash to go into 4wd high or low everytime i move forward to lock the hubs in they kind of grind and jerk as well. im not too sure what that could be either possibly the teeth of the hub or sway bars? because i do have a sort of knocking up front when hitting bumps also. any help is greatly appreciated!

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1999 ford ranger xlt sport 3.0l v6