1996 s-10 blazer 4.3 vortec. I usually park on approx.30 degree incline, front higher than rear. Never been off road ever. Last week rear broke traction put into 4wd. low made loud thud. idled up onto road,length of car. Went into neutral then 2wd hi. pulled to right after 10 or so miles so much smoke thought car was on fire,other drivers did too. Strong smell of trans fluid. Front diff low/ empty. Came out of vent tube attached to fan shroud. Did same thing next day, as I used 4wd. low to park car. just dripped off engine, no smoke/fire simulation this time. No check engine light What's wrong?