my blazer engaged into 4hi and i tried to put it back to 2hi and wont go, i can put it into neutral and it will go to 4lo and back to 4hi when i press the button, does anyone know what would be the proplem, i have a 3 button switch and i had vacuum proplems with the front diff so i think it could have messed up my tc vacuum switch

 

Shot in the dark, but try pulling your tccm fuse for 30 minutes, to relearn your tccm, then give it a try, otherwise, I am out of ideas. Sorry.

 

Need to read those trouble codes stored in the TCCM....take a look at the "4x4 no worky" thread in the DIY section. There are some other suggestions in that thread also.