I have a 2000 Chevy blazer zr2. Recently I noticed that my 4wd was not engaging. I would press the 4wd hi, the lights would blink and it would go back to 2wd. So I did some checking and found that the vaccum diaphram under the batter was shot, all dry rotted. So i replaced that, but that still did not fix the problem, although, i did get vaccum and the cable moved back and forth, I still did not get 4wd. So next I replaced the vacuum switch located above the transfer case that has the trhee hose connector going to it. after doing that, the 4Wd worked. I used it during the next snow storm. but after that, I noticed that the 4wd no longer engages.

Now when I hit the 4wd hi, the lights for both hi and low blink, but then it goes back to 2 wd. I do not hear any noise from the transfer case. but when I hit 4wd lo, the both hi and lo lights blink, I hear the transfer case engaging, but then all the lights go off.

Any ideas on what else may be wrong? It does feel that when I hit 4wd lo that it is in 4wd. but when I hit 4wd hi, i dont hear any sound like the transfer case is engaging. what else should i be checking?

I already replaced the 3 button switch on the dashboard and that did not correct the problem.


any ideas? could the vaccum switch had gone bad after one use... but, like I said, I do hear the transfer case engaging when I select 4wd lo. although the 4wd lo light does not come on.

 

It might be a bad brain box for the 4wd? I'd replace that as well. It is located on the passenger side kick panel. It just pulls right off no screws and I think the brain box has a few bolts (I forgot). Sometimes they get corroded and just need to be cleaned off.

 

I have the same problem every year. But the only "Brain Box Corrosion" is in my own head. If I would only remember to lube my 4x4 shift cable before winter each year I could probably avoid the corrosion lockup of the cable. It's really pretty simple to do. Remove the Battery and mounting plate. That's where the actuator is. Carefully disconnect the cable end and shoot a little at a time, PB Blaster lube into the end of the cable cover, between the cable and the cover. Let it run down into the cable about 5 minutes each shot for about an hour. I know this sounds real boring but , after about an hour the lube will work all the way through the length of the cable. Then just start pushing 2wd to 4wdHi back and forth setting still and in motion, below about 10 mph, and mine always frees up. If I could just remember to lube once in a while before it freezes up I don't think the problem would ever happen. Simple $6.00 fix for the can of PB Blaster at Wally world.