i have a 1998 blazer 3 button 4x4 have replaced encoder motor, tccm, bypassed vacumn diaphragm, replaced vacumn switch and front differiential switch still does not work

 

Do your lights, light up on the buttons? My buttons went bad and was stuck in 2 wheel drive. Removed buttons and re-soldered back of circuit board and been working ever since.

 

Yes they just flash and go right back into 2hi then after awhile of trying just click

 

Try what I said above or buy new switch from rockauto.com.

 

When the 4HI button is pressed do you hear or feel anything? Put the transmision in park or neutral to do this.
If you hear or feel a clunk....technical term there....then the encoder motor is working.

What do you mean that the vacuum diaphram has been bypassed? Have you checked...better yet replaced the vacuum lines between the engine intake, to the reservior to the vacuum switch, to the diaphram? Especially check in the left corner of the engine compartment...that is where the vacuum lines rot out for some reason.

 

I put a pull cable on the front axle cable to lock it in and when i press it i dont hear anything but i took the encoder motor off and tryed engaging it and the motor wheel did not move but the buttons lit up 2hi and 2lo