4Auto-4H Groan/Whirring Noise

[Adrian17]

2015 Silv. 1500 Z71

 

Might have double posted this on accident but Got the truck back in Feb. when the snow/ice storm hit here in Texas, on my way home I had it in 4HI and didn't notice anything then. Used the 4WD a couple of times at the job site at low speeds in mud and I never did notice anything then either. Well last week we had a pretty good amount of rain hit North Texas and on my way to job site I stopped and threw it into 4A before actually getting into the muddy roads and stuff. I drove on wet pavement for about 2 minuets and every time I gave it throttle it groaned, not a metallic noise just a groan or whirring noise. Put it into 4H and same noise not worse or better. Then put it into 2H and groan disappeared completely. I drove it slow and lightly until i reached the job trailer. I keep up with the fluids, I changed front and rear and transfer case about 2 months ago but had not used 4A or 4H since then. Fluids seemed ok, were not overly burned, the front diff was under the fill port a tad and did notice a small amount of buildup on the magnetic plug. Compared it to my 21 Silverado HC and a 2013 F150 and both are as smooth and quiet as can be although you can tell your in 4H/4A. Long story short you guys with the 14-18 trucks have any noises of any sort when in 4A or 4H? Did some reading and some guys are saying they do have noises and groans when in 4A or 4H and that its normal but im not sure it is, February feels like so long ago i dont remember feeling or hearing anything then. I jacked the front end up and spun the tires in 2H and nothing, put the truck in 4A/4H and nothing also, I did notice the front drive shaft was not spinning though when i hand spun the tires and had it in 4H but i guess thats due to the t-case not providing the rotation.