Repetitive noise under my 95 gmc

[Cdavis95Z71]

hey guys so I just bought a 95 Sierra Z71 and everything is in great shape but there’s a noise coming from under the truck that speeds up and slows down with the truck. I know it has to be after the trans because it continues to speed up even when the trans shifts. It’s sort of a bumping noise and it’s fairly loud. I got new tires mounted and balanced and an alignment and it’s still making the noise. I was wondering if any of you have had a similar experience or know what this is.

Thanks, Carson

 

[Schurkey]

U-joint? Transfer case? Rock in the tire tread?