Check your u-joints as well. Not just for slop though, I have seen 'em with zero slop, but, so tight you can hardly move 'em.

 

Well guys I’ve check all the things you have suggested and what I’ve found was the transfer case oil was pretty low, it’s suppose to run out of the top plug when you pop it open and I had to stick my finger pretty far down into it to touch oil. The oil isn’t nasty but it needs to be changed. I don’t have any atf+4 on hand so I’ll get some tomorrow and drain it then refill it. Hoping this was my problem with the noise it’s been making. Will know forsure tomorrow.

do you guys think this could have been the issue?

 

Maybe, but, I wouldn't hold my breath. Might wanna have a look at the snap ring that holds the output shaft bearing in place. They are notorious for breaking, and allowing the shaft/bearing to walk... which destroys the t-case. Just need to pull the tailshaft housing, and there it is.

 

drained the TC, took out drive shaft. The U joints were good. The bearing in the TC was good and so was the snap ring. So that wasn’t my problem. What do you think about it being the Over Drive? Could the OD gear be bad and that’s what the noise is? Since the noise is so specific?

 

You can use basic Dex/Merc in the t-case if you don't have +4

I think it's unlikely the t-case is your issue, but what does it look like at the drain plug? Any hard parts there at the hole? Lots of shavings/chunks?

 

I drained it and refilled with +4. No chunks and no shavings in it. Oil looked used but nothing bad about it. Still makes the noise. Could it be my over drive that I’d causing the noise?

 

I know you really want it to be your transmission but it's difficult for an auto to make the noise you describe.

Autos are essentially hydraulic propulsion so typically you'll get no shifting, poor shifting, shift flares or even bucking/shuddering....but a speed dependent grumble is really unlikely. Obviously it's not impossible -- I mean it's also possible I'll be abducted by aliens in the next 5 minutes.

Can you plug the rear slip shaft and get it up to speed on the front d/s only?

Your problem still says harmonics to me like from incorrect pinion angle or out-of-balance rear d/s or something similar. Your transmission mount is ok? How about engine mounts?

 

So get up to the speed where the noise is occurring, and hit the tow/haul button, or O/D Off button, (whichever it is you have) and see if the noise goes away.

 

tow haul button doesn’t work, I press it but never turns on of off. Any ideas how to fix that?

 

The button just sends a signal to the PCM when you press it. The PCM does the rest. If the button isn't working, probably broken wires.....