One of those late night moments where I'm thinking about things I have going on with the car. I'm 99% sure it has seen more road time with me in the three months i've owned it than the past few years.

When I get up to highway speeds, (40+) I hear road noise, sounds like it's coming from the front. Some vibration present in wheel, but again, its like the sound, only at the highway speeds. No vibration on the brake pedal when I press it. The tires are probably older, possibly balance or just old tires? But would they really contribute to that much audible road noise? It's definitely noticeable compared to sub 40,mph speeds.

Another concern I have is When I'm at a sustained highway speed (last time I noticed was when I was doing 70-80) and I abruptly lift off the throttle, I hear a clunk from the rear. Could that be the pillowball bushings? It does make the clunk when I press the brakes/going over bumps, etc as well, but the clunk from the rear at throttle lift off has me wondering?

 

When were your tires made? Old tires make more noise and ride hard. Modern tires are only good for 7-10 years max, other wise it could be a wheel bearing issue.

For the rear noise: Deceleration noise comes from a loose rear end, could be a number of bushings, most likely the OEM rear diff hanger rubbers tho.

 

Agree about the tires.
Are any of the bushings non-OEM? Have you inspected any of those bushings? Yes, firmer non-OEM bushings or worn bushings all contribute to drivetrain noise. So does most aftermarket bracing and engine mounts if you have any. Wheel bearings might also be something to look at.
And wouldn't inspecting your pillowball bushings instead of losing sleep and starting a thread with a title that has little to do with the topic make more sense?

 

try rotating the tires, if the noise/vibration moves, then its the tires.

if the car sat for a long time you can also check the tires for being round.

 

From what I've gathered by working on/around it, the car is completely factory, minus the wheels/tires. The noise on decel only happens right when I lift off the throttle, then nothing, like its responding to a shift in motion. It's almost like the pillowball noise we are familiar with, but it happens when lifting off the throttle abruptly at speed and then stops.

The tires are likely older, I'll have to look and see when they were made, No aftermarket bracing or anything of that nature.

 

How many miles are on the car and what condition is your power plant frame in? Lifting going from a throttle ON to a throttle OFF situation would cause the PPF to move the opposite direction it was being flexed before. It's likely fine but I'd check it anyway. Your diff bushings may also be shot. They are fluid filled from the factory and might have finally given up.

 

car has 22,000~, but it did sit for quite awhile. I haven't checked the PPF, but thats a good idea. I parked the car yesterday, went inside the library to study for hours, came back out, and the tire was flat, tire shop said there was no leak, it just separated from the bead, and that the tires on the car were from 2012 & need replacing. I'd be willing to bet that's part of the issue with the road noise and vibration, but the noise on throttle off, I'll have to check the diff bushings and inspect the PPF.