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More 4 wheel drive problems with my ’03 Blazer (UPDATED)

Am I glad that I fixed my 4 wheel drive! I’ve needed it a few times this month. The unfortunate part of this update is the fact that I now have a very defined “clunk” in the front differential. Of course, this is just speculation at this point simply by where and when the noise occurs.

The Blazer has a weak point in the transfer case (a snap ring that breaks causing a “grinding” noise), so that was my first thought, but quickly ruled out — it only does it in 4 wheel drive for one. If it were the snap ring, it would grind in 2 wheel drive and get better in 4 wheel, not to mention the noise would be coming from the rear seat floor (where the transfer case is) and not the front end (which is where the front differential is).

Anyway, I have to do a little more diagnostics with the guys over at the garage on a drier day to figure this out. I’ll keep you posted!


Wow! I thought I had updated this post to describe the problem as it was found by the guys at my tranny shop.

I really should get some proper terminology for the parts — anyway, as it was described to me, there is a set of “forks” in the transfer case that control the movement of a gear (gears?) for the various modes (2Hi, 4Lo, 4Hi). The forks have plastic (delron? nylon?) bushings that quickly wear out — this is an inherent problem with the transfer case of my particular year of Blazer — and cause the gears to not fully seat in their proper positions. This means that when you try to switch to 4Hi, it may not go in right away or, for that matter, when shifting to 2Hi it will seem to stay in 4Hi for a period of time, then switch to 2Hi with a “bang”. It may also kick in and out as you drive down the road, as mine did.

Again, I should really find out some more information on this problem. As I have said, I have a tranny shop in the family, so it was repaired and put “on tab”, so I can’t even tell you how much it cost to repair, but I will find out.

2 thoughts on “More 4 wheel drive problems with my ’03 Blazer (UPDATED)

  1. my truck goes into 4×4 but seems theres a vibration passenger side front also seems to disengage with a clunk same area . anything like yours?

    Kyle’s reply;

    Hi Dennis;

    Mine went into 4WD as well, and would only clunk / disengage once in a while. Of course, it got more frequent near the end — even without using it.

    It did appear to be coming from the front, passenger side, but it turned out it was the transfer case — so you never know. If it’s disengaging, chances are it’s more like to be transfer case related (unfortunately).

    The front, passenger side axle is controlled via a vacuum diaphram — if that was leaking and allowing the front axle to disengage (one side only – passenger), if would feel a whole lot different than a complete disengage.

    That’s about all I can really tell you — good luck!


  2. Kyle, seems like you are well versed in identifying and trouble shooting GM’s failed AWD system. my problem, no 4wd.. symptoms.. no light at switch, not even the 2wd light. Replaced the switch, no change. No click when the switch is turned to AWD/4H /4L.
    Removed the acutator, picked up the 12 little gears that went bouncing across the bay floor and reassembled. Used a scan tool and find that htere is no communication to the transfer case program. The engine codes will scan but no communication to the t/fer case. At this point I suspect the TCCM but can’t find it.. any thoughts.. thanks George V

    Kyle’s reply;

    Hi George;

    First, you should check this thread –>

    The first post shows the TCCM.

    Have you checked the fuses? Particularly UNDER THE HOOD? (See my comments from the same post –>


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