Hi, I’m having issues getting the blazer to engage the front differential. When switching to 4 hi it does light up and stays and stay lit I also hear a noise like a motor is changing gears, but does not engage the front differential. I’ve replaced the t-case switch, check my diaphragm on the vacuum actuator and still intact, also the cable does move an inch or so. My hoses all look ok too. What could be my issue. Thanks

 

If you see the cable pull in when 4HI is engaged, then the vacuum system is working properly and the problem lies somewhere in either the cable itself or the engagement mechanism inside the front axle (assuming that the transfer case is properly functioning). Either way, determining the cause starts with disconnecting the cable at the front axle to see if the cable moves properly at both ends.

 

So I was able to see that the cable does move on the vacuum actuator side and it does suck the diaphragm in and the front drive shaft does lock when in four hi but still no power. I did buy a new cable hoping that’s the culprit. Do you think the other end maybe disconnected or something? And my 3 push button says it’s in 4 hi and solid light.
Thanks

 

I put a new cable in and still no 4x4. The encoder motor is making a noise like it’s changing gears and I do here my relay clicking in my tccm. Do you think the encoder motor is bad?
thanks

 

With one front wheel off the ground, the cable pulled, and the transfer case locked in 4HI, you should not be able to spin the wheel that is in the air. If you can spin the wheel, check to see if the front driveshaft is spinning. If it is, then the transfer case is not functioning properly. If the driveshaft is stationary, yet the wheel still spins, then there is a problem internal to the front axle engagement mechanism.

 

I’ll try that next. If that’s all good though, would it then be the encoder motor? Everything I’ve researched kinda leads me to that. Because when I change from 2 hi to 4 hi it sounds like it’s just turning gears not just one good click. I ordered one already hoping that would be the culprit.

 

3-button or 4-button switch in the dash?

 

3 button

 

With the 3-button system, if you are getting vacuum to the actuator, then the encoder is doing it's job. The vacuum switch is activated by a cam on the shift sector shaft in the transfer case. The shift sector shaft is the shaft that the encoder turns inside the transfer case which is then responsible for the various mode/range changes inside the transfer case. So if the actuator is doing it's thing properly, then at least the end of the shift sector shaft is doing what it is supposed to be doing. That doesn't mean that there aren't problems deeper into the transfer case though, but you won't know until you see what the results of the one wheel up test is with everything locked in.

 

So I jacked up driver side and locked it in 4 hi and the tire could still turn. I haven’t tried to manually pull the cable to see if that would lock in or not, maybe it’s not pulling it far enough out?