Alright well another problem to add to the ever growing list with my 2002 4wd Blazer....well last week I started to here the sound of metal hitting metal as I drove, only when I was on the gas though, coasting nothing at all. Kept driving it becuase i need to get to work, well now I have a really bad shake in the rear end of the truck, and its getting louder everyday when I am on the gas. Also I jacked up the rear end and had someone put it in drive and hit the gas, very little to no noise at all....dont know if that helps determining what might be wrong....I did this to see if I could determine where the noise was coming from and easier. So far people have steered me toward a U joint.,....but figured everyone here might be able to direct me either agreeing on u joint or throwing a new idea in...THanks Jon ....oh yeah 2002 4wd 4 door LS with 81k miles on it .....

After searching and reading more posts I forgot to mention there is also a clanking sound when put in gear and hit the gas......

 

Is it a screeching sound? If so, I would suspect worn out u-joints.

 

Yeah I guess you could call it a screeching, someone described it as a chirping sound.....

 

Well i start with the easiest problem...U-joints...next in line to that if coming from the rear end would be wheel bearings...next after if your blazer has limited slip is clutch hub or spider gears are worn out/broken..only reason i say this is the fact you say that it happens when you press the gas and goes away when you coast...check to see if your diff is leaking most people never pay attention to the gear oil in their diff.. if it leaks or there is no fuil in there you can almost bet those gearsor bearings are gonebecause its not that hard to do...if your truck does not have lsd you could be looking at pinion bearings or side bearings..in a safe place try swerving left and right while lightly on the gas see if the noise goes away hope this helps..let me know if you need anything else...