almostamos

99 XJ w/ 231 tcase (jb sye, 6-pinion planetary, wide chain, etc) w/ 125k miles on it, behind a aw4.

I have a noise under my XJ that I cannot figure out.

-NO vibration comes from it
-Sounds like it is coming from the transfer case area
-Does it whether under load or not (shifted into neutral @ 60mph, no change)
-My son describes it best "sounds like a rattle snake under your jeep"
-I do not have a front driveshaft installed right now. If I put it in 4wd and drive it around, the sound does change a bit.

It is not the normal vibrating tcase linkage. I have a boostwerks kit on it. I've ordered a complete rebuild kit for my 231 just in case.

Any thoughts, ideas where to look?

-AA

InitialForce

Check your motor and transmission mounts.

I had this really annoying rattle noise that you would hear clear as day inside of the jeep and sounded like it was coming from right under me at the transfer case but I couldnt pin it down when I was outside. Turned out to be a collapsed transmission mount (looked good from outside visual inspection but when I took it off it was clear as day the rubber had seperated and the 2 metal shells very hitting each other) and 1 busted motor mount that made random rattle noises. Motor mount, rev the motor and look for movement on both sides. Like i said with the transmission mount i couldn't tell it was broken until i took it off and had the transmission weight off of it. Hope that helps

SteveMongr

Rattlesnake? Changes when put in 4WD without a front driveshaft?
Could be the chain dragging on inside of transfer case. When placed in 4WD, some of the slack is taken up and sound lessens. Just a guess..