4 wheel drive issue

Gidday all, I own a 1996 chevy silverado 4x4. I most recently tried to use the 4 high feature of my 4 wheel drive, pressed the 4 high button on the dash and it just blinks without engageing the 4 wheel drive? Is any mechanic or vehicle owner out there familiar with this problem or have a probable solution? Thanx so much.

A few suggestions, I’ve learned from a 2000 Blazer with an Auto-Trac 4wd system.

  1. The Transfer Control Case Module (TCCM) will freeze up if the 4wd drive is not engaged on a regular basis. A GM tech recommended unplugging the wiring harness at the TCCM, it’s located behind the right kick panel on my Blazer. It’s easier to disconnect the negative battery terminal for a few minutes.

  2. Check the vacuum hoses, after 10 years they were deteriorating on my Blazer.

  3. If it sounds like the transfer case is engaging, but the light is still blinking there may be a problem with the front axles not engaging. There is a vacuum control switch that controls the vacuum actuator that engages the front axles. The switch is located in the center of the firewall (on the Blazer) and the actuator is located under the battery tray. A bad switch will disable the actuator. I removed the vacuum hoses from the switch and spliced them together. The front axles then engaged and the 4wd light stopped blinking.

Here’s a few links that helped me.


Good luck,

Ed B.