Vehicle: 1993 Grand Cherokee 8.5" lift. Full Time 4wd. 318cid., 33" tires,

I am having an issue with a noise when I let off the gas. When I barely touch the gas it goes away. I feel no unusual vibrations. I removed the front shaft and drove it around, no change. I then removed the rear(after installing the front <img src="/forums/images/graemlins/nana.gif" alt="" />) and drove it around and no more noise. I do not think that I have a slip yoke eliminator. I was wondering do you all think this could be coming from something internally in the transfer case, or coming from the rear end? Either way it has to have some sort of preload on it (i.e. letting off the gas) to make the noise. It almost sounds like a loud siren. Thinking of just installing a rear locker and see what happens since I want one anyway.