After I purchased my used 2003 Z-66 with 241K miles back in February, I began replacing missing or worn out parts.
One of the items I found missing were all four bumps stops.
I later found that all four bump stops were also rotten or missing on my 2004 EXT at 236K.
Both the 2WD Z-66 and the AWD EXT use the exact same parts.
I have now replaced all eight bump stops between the two trucks.
What I found was, the front bump stops are in constant contact between the two points of the front suspension on a non-lifted truck while at rest.
The rear bump stops do not rest on the lower suspension and ride a good 3-4 inches above the axle while at rest.
At no time did I ever have any sort of noise coming from any corner of either truck while driving that would indicate I was missing a fully functional bump stop.
I suspect it would take quite a dip in the truck body while driving to made any kind of metal to metal contact, as I have never once heard any such thing from my trucks.
The bump stops on the 1500 series trucks are one of the easiest repairs one will ever do on their truck.
The bump stops simply sit in a retaining cup that is welded to the upper frame.
A couple of mine were totally missing, while the rest were so rotten they served no purpose.
I took a screwdriver and dug out the rotten remains and used the same screwdriver to help wedge the new bump stops into the cup.
There were no bolts involved.
Here are a couple of pictures to show what the rear bump stops looked like before and after the repair.
Since your Avalanche is a Z-66, it came with self-leveling Nivomat rear shocks.
How old are the rear shocks?
Under normal circumstances, a functioning Nivomat shock will always be under some load since it's design is to provide automatic lift as needed to the rear end of the truck.
When driving, if the rear of the truck is dropped due to a load, the Nivomat self-leveling shocks will automatically pump up in an attempt to keep the rear of the truck at a constant, predetermined level.
If one or both shocks are worn out or otherwise defective, it may be possible that the shock could make some noise since it will not be under normal pressure.
As mentioned above, worn out, broken or missing sway bar end links can also be a source for rattles and other noises.
Getting the truck up on a lift and working it over with a pry bar will sometimes find loose components.
