Buzzing noise from rear of '05 tahoe

When we start our 2005 Tahoe, after the engine turns over and we are just sitting there, there has always been a buzzing sound (sounding kind of like a hammer drill) coming from the rear of the vehicle that last for about 2-4 seconds, and then it stops. Recently, the same noise noise has been occurring during normal driving. Last night it occurred several times while driving a short distance. It came on and stayed on for several minutes before stopping. I am fairly certain the noise is being generated by a small black cylinder located behind the drivers side rear wheel. I could feel it buzzing when the noise occurred, but I don't know what that part is and can't find it in any of my manuals. No codes are being registered on the computer and there is no drivability issue here, just the noise. Can someone help me diagnose this and possibly prevent a future problem? Thanks!
Silvio

From here, it sounds like your air compressor pump that controls the air pressure in your air ride control system. Yes they can be noisy, and can run more often if you have an air leak. Just knowing what it is will probaby satisfy your question. It probably cycles on after each ignition cycle, depending on ride height and/or if you have a small leak.

See if it makes the noise the next time you load a couple hundred pounds in the rear.

I appreciate the post. Yep, I now think it is exactly that-the auto ride air pump-cycling on and off. In fact, the other day when it went on several times while driving, we had a couple hundred pounds of grain in the back (we usually don't haul anything with this car) and it was pretty cold outside. So, sounds like it is a normal sound. If there is a leak somewhere in that system, where would I look, or how would I troubleshoot the leak? Does the air hose that comes off the pump supply the shocks with air? Thanks.

I appreciate the post. Yep, I now think it is exactly that-the auto ride air pump-cycling on and off. In fact, the other day when it went on several times while driving, we had a couple hundred pounds of grain in the back (we usually don't haul anything with this car) and it was pretty cold outside. So, sounds like it is a normal sound. If there is a leak somewhere in that system, where would I look, or how would I troubleshoot the leak? Does the air hose that comes off the pump supply the shocks with air? Thanks.

if these are the originals [lifts] this is about all the life you get ...

use a spray bottle with dish soap/water mix spray the fittings/shocks look for bubbles..

I would make this decision quickly with your correcting this as this air pump is not designed to work all that much.

installing non OEM air ride system, is possible..this would be less costly.

if these are the originals [lifts] this is about all the life you get ...

use a spray bottle with dish soap/water mix spray the fittings/shocks look for bubbles..

I would make this decision quickly with your correcting this as this air pump is not designed to work all that much.

installing non OEM air ride system, is possible..this would be less costly.
Really you don't even need the air ride, being it's for the rear only. I'd say make a $60-80 dollar run to the parts store and get some Monroe shocks (the more comfortable rding shocks) and call it a day. You can turn the air pump off and it'll sit there and do nothing - at least until you want to get some air shocks or save up for OEM air shocks.

I know a guy who had a Cadillac Deville with the air ride, he removed all of it and put coil over struts and shocks. He said it didn't ride like it used to it but it was a cheaper alternative to $700 OEM parts per side (Front/Back)