My 4x4 still doesn't work on my 98 4x4 blazer. Replaced transfer case switch, vac lines. Actuator and still no 4x4. What do I check next?!encoder motor?? Tccm??. I hear a clunk when I put in 4lo but it doesn't engage... I'm all out of ideas so any help or advice would be much appreciated

 

When you hear the "clunk" does the front driveshaft engage? If the transfer case engages, the front shaft should not spin (without the vehicle moving).

If the shaft still turns by hand after you've hit the button for 4wd, then the t-case isn't shifting properly.

If the shaft doesn't turn, but still no 4wd, then the problem is in the front axle.

 

Check to make sure your actuator cable isn't corroded and sticking. It plugs into the vacuum actuator and when vacuum is applied, pulls to engage the front differential. If that checks out, clean the connections on your tccm. Its located under the passenger kick panel.

 

Ok will do thanks guys I'll keep you posted

 

As mentioned above: pull on the actuator cable with pliers to ensure the cable is not stuck. You can try pulling the cable and then either lock the cable with vise grips or something and check the front axle engagement. This will determine if the front axle clutch is working.

Next you could remove the encoder motor and engage the t-case with a wrench. This will determine if the t-case is working. Then with the motor out, hit the 4HI and watch the motor, it should rotate. However it could just be weak and not able to engage the t-case. Clean the electrical contacts of the TCCM and when re-installing the encoder motor be sure to align the t-case and motor.

This should determine what part is not working correctly.

 

make sure your vacuum lines are routed correctly. seen it where someone mixed up the vent line with one of the vacuum lines