Push button 4x4 model. Rear drive only. Control module clicks when buttons are alternately pushed from 2wd to 4hi but no noise from shift motor/transfer case signaling engagement. Shift motor does move gears from high range to low range and back when the 4hi and 4low buttons are alternately pushed. Any ideas?

 

There is a vacuum actuator under the battery tray, but more than likely it's the encoder on the transfer case. Pretty common.

 

THANKS for the reply. Sounds like the encoder then. Guessing that since the shift motor moves the hi and low gears it's getting vacuum. So is the encoder replaceable by itself or does it come with the shift motor?

 

Finally got the Blazer into the garage (bit of a snow problem)and on jack stands. Seems it's not what I thought it was. Everything is working as it should with the front driveshaft engaging and disengageing. The front axle is not engageing. Anything else besides the actuator and shift cable to suspect?

 

IIRC, the actuator under the battery activates the front dif, so I'd check that next.

 

Ok The actuator works. I disconnected the cable at both the actuator and the axle. It slides in it's housing fine. But with the vehicle running in 4hi mode there seems to be the slightest bit of binding at the axle end when I manually pull the cable to make the engagement. The actuator will do all but the last 1/4" maybe. I can squeeze and manipulate the blatter to make the engagement though. Tomorrow I'm going to pull the cover at the axle again and see what I can come up with.

I do APPRECIATE the info!

 

If the buttons just blink when you put it into 4wd and then go back to 2wd, unplug the 4wd module inside the passenger kick panel and plug it back in. If that doesn't work, get a new 4wd module. I've personally had this problem a few times.

 

My module's under the dash. Everything works fine to engage the 4x4 mode. It's the engagement at the axle that's the problem. I'm leaning towards a weak actuator or weak vacuum to it. Anyone know how much vacuum should be at tht actuator?

 

If your tired of messing with it http://www.4x4posi-lok.com/app_chevy-s.html

 

THANKS but I already have it in my favorites.

I can only confirm one bad part so far. The transfer case vacuum switch. Got one last evening and will put it on later today.