Weird Sound; Exhaust, Tires...I have no idea.
 

Alright, so I'm having some weird sound coming from my truck. It's basically a loud "whomping" sound. It is louder and faster when I am on the highway, I'm assuming due to higher speed. My buddy told me it was the tires being worn down, but the sound dies down when I take my foot off the gas pedal. When I accelerate, it's not as apparent either. And when I apply the brakes, it's not there. Only when I am at a constant speed with pressure on the pedal, it's loud and repeating, whomp-whomp-whomp-etc. I'm thinking it might be the exhaust. I have a tiny muffler and the exhaust spits out in front of my right-rear tire(I've heard that be called a "side-dump), which is where it feels like the sound is coming from. Not necessarily "sounds" like it's coming from, because it's so loud it could be from anywhere.

Does anyone have any advice, or have any experience with this? Any help is appreciated, I'm more or less at a loss.

EDIT: I looked into it further, and found that it might be the caliper anchor plate bolts or lugs are loose. Anyone have any similar experiences?

you have a blown internal belt in 1 of your rear tires

usually the rear paasenger tire is the first to blow since it is the tire that is under stress during acceleration . blown belts are a common problem in tires on that specific tire location

Why does the sound die down when I apply the brake?

the weight of the vehicle plays a big part
slow speeds you will not feel any vibration , but hard acceleration , you will feel the whomp whomp

i had this problem with my factory tires , the acceleration force on the right rear passenger tire far exceeds any force placed upon the other 3 tires during acceleration

any tire balancing shop can determine how bad the internal belt has slipped inside

look for any abnormal bulges on the sides of the affected tire

I will do just that.

It's more of a sound than a feeling, though. It's loud as ever and fills the cab. And it's consistent when I'm holding down the gas pedal, travelling at a constant speed. During braking or acceleration, it's not as apparent.