4x4 Will Not Work
 

I know what you're thinking, you've seen a billion of these threads on here, and they all have the same solution. Well I've seen them all too and I still have no solution. Here's my problem: I have a 2003 Chevy Blazer ZR2 and I don't have 4 wheel drive. My actuator under my battery pan is brand new, as is the tension wire that runs to the front diff from it. All of my vacuum lines are checked and they are good, and the vacuum switch on top of the transfer case is new as well. My transfer case AND my encoder motor both work flawlessly, as does that little electronic box behind the passenger side kick panel because I can hear them both working. Also, when my Z is on the lift, and its in 4HI in either Drive or Reverse, the front drive shaft moves, but the front axle does not. I also have a parts Blazer that I've been swapping parts from, so I tried its vacuum switch and also its actuator and that did nothing for me as well. I also tried tightening the tension wire down where it goes into the front diff just for ****s and giggles, and still nothing. I've basically narrowed it all the way down to the diff itself. Is there something in there that would limit my front axle from engaging? Any help or tips you can give would be greatly appreciated, because I'm at the end of my wits with this thing and mudding season is fast approaching

There's a coupler in the passenger side axle tube. The cable pulls a collar across two gear, connecting the axle shaft, and giving you 4wd. On mine, one of the gears was chewed up, preventing the collar from engaging

This is what the assembly looks like:
https://cimg1.ibsrv.net/gimg/blazerf...6cce28b52c.jpg

This is what my gear looked like:
https://cimg4.ibsrv.net/gimg/blazerf...861edc8eb2.jpg

I replaced the gear. I believe it's called a "connector." It was around $70, I think.

To access this, you will need to split the passenger control arms, and remove the steering knuckle, remove passenger cv shaft, then you can remove the axle tube
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cleburne red shared what I was going to suggest; the coupling gear in the front axle. This can get worn down and not engage the right side (passenger side) output shaft to the differential. With the left side not connected to the axle and wheel, the passenger side output to the differential rotates freely, just like it would if it were engaged to axle and the passenger side wheel was on ice the the drivers side was on dry pavement. (The front differential is an "open" one so that there is no locking mechanism.)

When you say you tightened the cable, are you referring to pulling on it yourself? Because if you did that and still nothing, then it is likely the gear cleburne red identified.

Be sure to report back what you find and/or learn.

On EBAY you can find an overhaul kit for the shifting mechanism in the above photos. I got mine for $100 and free shipping. It comes with all the parts to do the job.

This is what it is called on EBAY:

GM7.25IFS Disconnect Kit 1997-2004 S10 S15 Chevy 4X4 Front Axle

This kit is from G and M Gearworks in Springfield, MO.

It will fit any GM product during those years. S10, Blazer, etc...

I have a 2002 S10 Crewcab and bought my kit from them.. Just waiting for good weather to rebuild mine...

Goodluck..

Bill