Inherently, it is due to the design of the transmission....
The 700R4/4L60E transmission has a design flay that will rear it's ugly head if it is in a heavy vehicle with a long drive shaft. No matter what the calibration, etc, etc.... If something is changed and one tries hard enough, the noise can be found.
When the trans shifts from 2nd to 3rd, it's very busy. It first has to release the 2/4 band and then apply the third clutch. In an automatic transmission using planetary gears, one can never use three seperate holding devices.......unless you want a hydraulically controlled Park! To prevent the main shaft from locking to the case, there has to be a bit of time-delay built in.
Now look at the stackable tolerances from the crankshaft to the wheels......gears in the trans, u-joints (albeit very minimal), and finally in the ring/pinion. Under certain circumstances (namely a 2-3/3-2 shift) all of those tolerances are unloaded, then loaded with a lot of mass. This unloading/loading can be heard through what is inherently a very large speaker.......the big ole hollow driveshaft. Don't think for a minute that GM added the rubber floor mat for Avalanche owner convenience.......it's a huge sound absorber trying to minimize the noises heard through the prop shaft.
There are numerous TSB's and PI's in the GM system that addresses this. However, there are really no known cures for it. Some are worse than others due to differences in stackable tolerances, specifically what the backlash is set to in the rear diff. By no means try to have that tightened as it almost always turns into a rear axle whine around 30-60MPH that is REALLY annoying! If it REALLY REALLY bothers you, one can take the propshaft to a very good machine shop, have the end cut off and install a press-fit cardboard sleeve, put the end back on and hope for the best. Some folks will advise to foam the prop shaft, but usually ends up with a nasty vibration as nobody really gets it done right....
Bottom line, a change in calibration will only hide it, and it can eventually be found again if one is anal enough. Nothing is being hurt and actually tells you that the third clutch is not slipping a bit! (or the 2/4 band is holding great, depending on if up or down shift).
However, if anyone hears it in a 2500 Av......take it straight to the dealer and ask them to look at the sprag which is getting ready to puke.
Enough of my incessant ramblings.....lol.