That is pretty normal behavior for the detroit in s short wheel base rig. Wait until he is driving it in the rain. I have had my rig do lane changes as the locker engages then dis-engages when I let up off the gas then accelerate.
Just rememeber the locker engages when power is applied and dis-engages when you let up off the gas. Once you understand that then you can modify the way you drive. You get used to it.