'Grinding' sound when accelerating

[qxx]

I've had the car about 4 years and this sound has always happened under these specific conditions:

For example, when I'm driving on the highway at 40mph or so and I try to speed up, if I keep my foot on the pedal to accelerate, there is a 'grinding' type sound. If I take my foot off the pedal for a second, then put it back on a bit more gradually to speed up, no grinding. So, if I jam my foot on the pedal to speed up, the grinding comes and if I keep my foot down, it'll get louder and almost worse. The second I left up my foot and take a more gradual approach to accelerating, it does not grind. Very odd. I cannot think of what is causing it. Like I said, it's been going on forever.

Any suggestions?

Edit:

It's 4WD (auto/low/hi)
2 new wheel hubs, the sound has been there before and after both.

 

[shoalcreek5]

Could be: rear wheel bearings need to be repacked; pinion in a differential worn or has too much play; one or more u-joints going bad; cv joint on front drive shaft going bad; one or more front axle cv joints going bad; broken or loose motor mounts; broken or loose transmission mounts; slightly sticky brake calipers; loose brake shields; or, for the worst case scenarios, either nearly worn out gears in the transmission, transfer case, or a differential or a grinding crankshaft/camshaft bearing.

 

[Joseqew]

I've had the car about 4 years and this sound has always happened under these specific conditions:

For example, when I'm driving on the highway at 40mph or so and I try to speed up, if I keep my foot on the pedal to accelerate, there is a 'grinding' type sound. If I take my foot off the pedal for a second, then put it back on a bit more gradually to speed up, no grinding. So, if I jam my foot on the pedal to speed up, the grinding comes and if I keep my foot down, it'll get louder and almost worse. The second I left up my foot and take a more gradual approach to accelerating, it does not grind. Very odd. I cannot think of what is causing it. Like I said, it's been going on forever.

Any suggestions?

Edit:

It's 4WD (auto/low/hi)
2 new wheel hubs, the sound has been there before and after both.

My 2018 xlt does the same thing I can gradually speed up but if I try to accelerate hard it starts grinding