Quote Originally Posted by Matt_ View Post
The ELSD's are actually a gyropump within the diff that creates hydraulic pressure when there's differing wheel speeds. The electronic version of the diffs is actually a solenoid valve which moderates how much of the pressure is applied to the clutches... full open on the valve results in a "locked" diff.
So what is the "whirring sound I hear when I shift in/out of 4LO? Is that the transfer case? I assumed it was the diffs since I can still go into 4LO but no longer hear the sound.

Quote Originally Posted by Matt_ View Post
Remind me tomorrow evening and i'll pull out my service manuals to see if you can run a test using a DVOM to see if the solenoid in the diff is stuck or not (usually you can do this by checking the resistance).
I have a DVOM and will remind you tomorrow.

Quote Originally Posted by Matt_ View Post
When was the last time you changed the diff fluids? I'm sure MOAB trail riding with some 33" tires put those axles to work... HARD... may be worthwile getting some fresh fluid in there with some friction modifier. As the fluid starts breaking down you'll get more "chatter" than normal from the clutches.
I had it changed not that long ago--January, I think.