Tire noise?........

[davemc53]

For the past year my '89 3.9 4WD has been making a noise in the rear that sounds like bad tires, but I don't think that is the problem. The sound is a whining sound that gets higher and lower pitched as I speed up and slow down. The transmission has been fine, so I don't think that is the problem.
It almost makes the same sound as when it is in 4wd, but it is not in 4WD.
Any ideas?
Thanks,
Dave

[Dakota00]

check the fluid level in the rear end. It would be a good idea to change it, if it hasn't been done yet.