4 Wheel Auto not engaging

I have a 99 blazer that will will switch to 4 Hi, 4 Lo and 2 Hi. But will not go into 4 auto anymore. I replace the dash switch and still no luck? The blazer has 104000 on it. Any ideas where to look next.
Winter is coming quickly and my transam doesnt like snow!
Thanks,
Mike
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replace the front wheel actuator with the new and improved motor driven ones. about 100.00 john

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Thanks John,
I will look into the actuator. I noticed yesterday that it did actually go into 4 auto, but today it is not working again. Could this still be the actuator?
thanks,
Mike
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Archenon wrote:

I think John is mistakenly thinking about the full size trucks. The actuator on the Blazers is a vacuum actuator that "pulls" the diff into engagement, the full size trucks use an electric actuator that "pushes" the diff into engagement. There was a change up to the actuator for the full size, but nothing that I know of for the Blazer style of actuator. If you are getting 4lo, 4hi, and 2hi, but not 4hi-auto....I'd be looking somewhere else other then the front diff. Are you truly getting all 4 wheels turning when in 4hi?
Ian
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The truck goes into 4 hi when you hit the auto switch. It definitely is in 4x4 when it is in 4 hi.
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snipped-for-privacy@msn.com wrote:

So you are saying that your complaint is that the light does not come on in the auto4hi position?
Ian
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It is my understanding that 4Hi and 4 Auto are two different modes. During the last 4 years of ownership I have used both quite a bit and 4hi feels much different then 4auto. I dont know the details of the difference. But when I hit 4 Auto now it goes into 4 Hi and feels like 4 Hi has always felt.
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