Problem with 99 Jimmy

Hi,
I have a 99 GMC jimmy 4x4, 91k miles 4.3 V6, I have had this problem, which didnt start untill the person I bought the truck from took out the Transfer
Case Control Module, because it quit working. Anyways the problem is (besides no 4x4) I have a pulsating humming noise in the front end (kinda like a wheel bearing hum, but it pulsates, not constant).
I have checked the wheel bearing by taking ahold of the tire at the 12/6 positions and the 9/3 positions and wiggling the tire, it is tight NO play, I've checked the tires, I even put the spare on the front to see if that took care of the problem, but it didnt. So what else could I check out?
Is there a way that the X-fer case is some how messed up because the Control Module isnt in the vehicle? Or could be transfer case maybe be out of oil?
Any suggestions would be helpful. Thanks
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Sounds very similar to the what noise I am hearing in my '99 Blazer. I still think it is the wheel bearings even though the no play can be detected in the wheels. I'm going to replace my bearings soon to see if that corrects the noise or not. I've attached a link to the thread that I dicussed this in:
http://groups.google.com/group/alt.autos.4x4.chevy-trucks/browse_frm/thread/e78056e78b42c6c6/d95ed2821e69defe?hl=en#d95ed2821e69defe
Thanks, John
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If I had the extra 170 bucks to throw away changing a part that may not be needed I would do that, let me know if the wheel bearing fixes your problem, ours hasnt got any better or worse since January of this year and we have put 8k on it since then.

e78056e78b42c6c6/d95ed2821e69defe?hl=en#d95ed2821e69defe
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