I have a 1991 auto v6 pickup with eletronic 4wd. I have an intermittent problem where my car wont move in 2hi and 4hi, but it will work in 4lo. I can feel each gear enguaging when the car is in 2hi and 4hi, but it slips, only enguaging ever slightly. I'm wondering if this is a transmission problem or transfercase problem, or maybe something else. This only happens sometimes becuase It will be working and shifting perfectly fine one moment and the next day, i get nadda.