The vehicle is a 99 Chevy Suburban 5.7L LT, when I hit 55mph I start getting this loud vibration, sounds like loud bass.

What I've done...
got up to speed and put it in neutral- no change
turned off the vehicle going 60mph- no change
went down a dirt road going 60mpg- less noise but still there.

I'm thinking it's a tire issue, the tires are not that old but have dry cracks between the treads.

 

Those looks bad cracks. Start with your tires rotated and balanced, then check steering wheel for front tire shake and drive shaft for rear tire shake. Alignment might be issue for tire wear.

 

zoom out so the pic shows the entire tread.


most common tire noise is due to toe misalignment which leaves a saw tooth pattern either on the inner or outer part of the tire. the noise will sound like a growl, similar to a bad wheel bearing.


does the frequency of the noise change with vehicle speed?

 

The noise is most noticeable from 55 to 70mph. The tires were just balanced back in February.

 

where do you feel the vibration; thought the body of the vehicle, just the steering wheel ?

 

I had a Nissan truck do something like that. the welds on the roof brace were missing and the roof was flexing.


common vibrations are tire or driveline related. if the tires check out, inspect your driveshaft ujoints.

 

The vibration is heard and felt through out the entire vehicle. I checked the u-joints and they feel solid. I went 65mph, put the vehicle in neutral and shut off the truck, thus taking out all components others than the tires. The vibration was still there so I'm thinking it's the tires.

 

did you remove the driveshaft to check the u-joints?

 

Those tires look dry rotted and have issues. Definitely not road safe. American or foreign brand? no name brand or major brand?

 

I inspected the u-joints with the drive shaft still on the vehicle. I'm leaning towards the tires being the issue. I'll keep you guys posted. Thanks for all the help