Why would my 2005 Silverado 2500HD duramax start making a hum noise on slow down on 2005 Chevrolet Silverado 2500 HD

This noise is in unison to the rpms and tires rolling on slow down. There is nothing in the tire lugs or hung up underneath. It was never there before and cant be good. No grinding or cluncking. more like extra resistance as the vehicle decelerates

by in Gresham, OR on September 30, 2013
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1 answer 3 comments
ANSWER by , October 01, 2013
COMMENT by , October 01, 2013
No, There are no check engine lights that have showed up. I do have a Diablo Sport Predator model Engine tuner/Analyzer. Would that show any codes that may relate to the noise, that aren't coming with a light or visual indicator?
COMMENT by , October 01, 2013
that maybe your issue. try taking it out and see what happens
COMMENT by , October 01, 2013
This is a portable unit that plugs in down by the emergency brake pedal. It is not in now, but I will run a check today and let you know if any codes come up. Thank you. I plugged in the analyzer and ran though the diagnostics and there were no codes. I did a road test on slow down and took it from Drive to "N" the noise did not change. It was slowing at the same pace the wheels were rolling. It does not sound or feel like wheel bearings, more like something in the front middle of the chassis. Some kind of guide or bearing mabe in the transfer case area. I can yake it to a local shop but thought it may be something that was a problem you had seen in other Silverado durmax trucks with an Allison Tranny. This truck has been excellent and has 105k on it. Still has original brake pads.