Does anyone know if this is a U joint problem or a transmission/transfer case problem?

Hi everyone please help. Whenever I go into reversing and brake I keep hearing this sound. Please tell me it's a u joint problem.

2004 Ford Expedition XLT 5.4 L
251,790 miles driven

I uploaded the video here.

https://youtube.com/shorts/feL2ZSvTV...EbL--0GA1aB0zK