Calling all GLP mechanics--gmt400 (Diesel_Tech where are you?)

So, we get our health advice from GLP why not health advice of sorts for our vehicles.

My old buddy Diesel_Tech who I normally asked has either changed his name or is no longer here.

Ok, so here are the bullet points

1997 Tahoe Z71 2 door

Obviously has 4wd and all the offroad goodies offered by GM.

Now here is my problem.

Whine/hum that starts around 20 and stays constant under load. The hum/whine disappears when I let off the gas.

I feel a slight vibration in the gas pedal as well and it does seem to change pitch when I slalom the truck side to side at speed.

Now, I know most will say its my rear end pinion or carrier bearings. I thought this too and it still very well may be but I emptied the fluid and no shavings or glitter indicating a rear end about to grenade.

I changed the rear axle bearings and seals to rule them out and no avail.

Basically my symptoms are a blend of wheel bearing and rear end.

How the f--- do I pinpoint what it is? I can figure out how to repair just about anything on this truck but when symptoms match 2 or 3 possible problems....that's when things get a little iffy for me.

I really hope its a bearing and I'm not stuck rebuilding, shimming, and correcting backlash on a new rear end.

The rear end is RPO code GT4 which is the 30 spline 10-bolt with 3.73 gears and posi/locker