Try changing the seal in the transfer, before you attempt the bushing. I´ve never changed the bushing in a 242, but have done a 241, imagine they are close to the same.
If the seal doesn´t hold or wears out quick. Time to think about changing the bushing.
Grinding or growling sounds travel through the whole driveline, often hard to figure out exactly where they are coming from. Where you hear the noise, is often not where it originated, but where you can hear it the best.
Some common problems are bearings, U-joints and differential parts.
Some of the places I have found, in order of probability are, front driveshaft U-joints, driveshaft U-joints, wheel bearings, spider gears, carrier bearings. There are others. On occasion, I´ve had to put the XJ on a lift and run it at 15-20 MPH, with some kind of hearing help. to nail down the source of the noise. A little brake pressure to load up the driveline often helps, in diagnosis. If you put it on a lift, be extremely careful of rotating parts, hair clothes what not, can cause catastrophy.
My NP242 whines pretty good in full time, never seemed to hurt much.
The double U-joint (carden) on the front driveshaft (unless you have a CV joint) rarley gets greased, needs a special fitting for the end of the grease gun.