When i go to put my 91 S'-10 blazer with the 4.3 and auto trans with lever action 4x4 into 4hi or low it dose not work. the front drive shaft will lock in but thats all that happens. the truck has no 4x4 even with the drive shaft locked in. I was thinking about replaceing the 4x4 indicator Sensor and the vacuume accuator this weekend an try that. if that dont fix the problem what else will? i have no vacume leak or cracks in my vacume hose's, and yes the transfer case is enguaging


Help me please

 

I just had problems with my truck too, I kinda worked around it, try engaging LO in revese if it does engage then try HI if that works put in drive right away because when I did that and left it in revese it sounded like the gears were grinding but after re trying it and putting it in drive right away my 4x4 worked fine.
I ended up fixing the problem when I replaced my intake gasket however I have no clue what I did that fixed it.