Borat

Hello, Borat here. I have 2014 GMC Sierra 1500 with 80,000 miles. HIGH FIVE! But it have problem. I have noticed sometimes when accelerating(on ramp getting on high way) there is a whining/gear grinding type sound. I can only force it to happen by punching the accelerator and causing it to shift from 4 or 5 into 2 or 3. It sporadically happens at low speeds but I’ve been able to replicate it happening around 70mph and hard acceleration. See video below for sound. https://youtu.be/9L2obt0J2eg

Has anyone ever heard this sound when their truck is shifting gears? It’s almost like a grinding and howling sound and happens only when I’m accelerating. I think it is transmission related since it’s only when gears are shifting. I brought it to dealer but they could not replicate. I have a 2014 GMC Sierra 1500. 80,000 miles. I’m concerned the transmission is going to give when I have little time left on powertrain warrantee. B2861495-01B5-41CA-B540-25A3A01CB590.MOV