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Keep on truckin
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Discussion Starter · #1 ·
1999 GMC sierra Z-71. truck produces a low groaning noise at speed. found out the t-case is stuck in 4wd. front axle engages and disengages normally but driveshaft is locked to t-case. when each 4wd button is pushed t-case motor shifts to that range. what would be possible causes? need some helpful information by tomarrow afternoon. thanks
 

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Hmm.. I wish I could say for absolutely certain, but I think that when my 99 was doing that, I had to replace the encoder motor?? I think...
 

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Built not bought!!
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I've got a 2001 gmc 2500 with autotrac and the front driveshaft spins all the time, always has, figured it was normal. you might have a bad u-joint or output bearing
 

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Keep on truckin
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Discussion Starter · #5 ·
i'm not very familiar with autotrac thats y i asked. i'll check u-joints
 

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My front driveshaft was always engaged when I had the autotrac case. It did go through u joints pretty regularly. The front driveshaft is almost in a perfect straight line with the front axle so the u joints often froze up and started to vibrate a bit. I did also have to put 2 encoder motors in it in the 175,000 miles that I owned it.
 

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Keep on truckin
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Discussion Starter · #7 ·
well i've determined that the u-joints are toast and the slip shaft is siezed in the t-case. gonna fix that and see what happens
 
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