Stuck in 4-Hi

98 Blazer-70K: Intermittent problem with T-case staying in 4-Hi when selecting 2-Hi. It might take a couple of miles and several tries before it finally shifts back. The indicator lights work normal.
Thanks in advance for any advice.
brody
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sounds like the encoder motor on the xfer case is going out.

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brody wrote:

Start with some simple things, are all four tires the same basic diameter? In other words, are they all worn about the same? If you have tires on one axle that are worn more then the other, you can experience driveline binding which makes it hard to shift out of 4hi.
And there have been lots of encoder motors problems on these models. It may be on the way out.
Ian
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wrote:

As a matter of fact the tires *are* worn at various amounts. But yesterday I jacked all four wheels clear and tested it that way. It went into 4-Hi immediately but would take about ten seconds or more to go back to 2-Hi. Maybe that's normal?? Shouldn't the 2-Hi light be blinking during the shift? It just goes on right away. Guess I'll just wait and see if it gets worse or something fails completely. Looks like a bitch to replace that motor. Thanks for all the advice.
brody
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brody wrote:

Thanks for the further diagnosis. From your description, you may indeed have some problem at the front axle. You might want to try this, jack it up again, shift into 4hi, let it idle so the wheels are turning. Then while you shift into 2hi, have someone watch the front driveshaft. If it stops turning right away, but it still takes time for it to achieve the shift, then that would sound more like a problem with the front diff actuation. The encoder motor can shift the t/case very quickly, but the shift is not considered complete until the front differential is disengaged. If the front diff is slow to disengage, then you need to determine whether it's a mechanical problem, or a vacuum problem.
Oh, it's not hard to replace that motor, but there are a few tips to make the job easier.
Ian
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wrote:

Hi Ian,
I did that. I can hear the motor actuate immediately when I select 2-Hi, but the front wheels and drive shaft continue to turn for ten to fifteen seconds.
brody
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