My 2002 Jeep cherokee is making a grinding noise when put in 4wd. What can be wrong?

so what 4wd is there.
part time?
or full time.
we cant guess what options you paid for new.
if part time,
stop driving in 4wd on dry pavement,only on ice or dirt.
if full time. then say so.
full time 4wd, or are you in lock mode. do not do that on dry pavement.

pads may be warn down and grinding on the discs.

could be a bad wheel bearing making the grinding noise. not that firmilliar with the grand cherokees,but that shouldnt effect the transfere case not shifting.

Give a try by change your transmission/filters and Transfer case oil.

Sounds "used and abused"!!! Likely you have more than one problem. Transfer case may need linkage adjustment or rebuild. Grinding from where? Wherever the noise is, look for a problem. Pulling can be from any number of front end component failures. Your best bet is to give everything a careful inspection or have a reliable shop go over it for you. There are so many variables in this I couldn't possibly give you any real answers!!!
good luck!

sounds like you have a problem with one of your lines on your power steering or one of its components. the grinding noise could also be one of your pulleys that have gone bad too. check your steering assemby gear box.

Sounds like the transfer case is not fully engaging itself. you will have to check this out. This will only cause more damage if left alone. make sure the wires are connected and tight. if the wires are OK, the internals are likely to be malfunctioning. replacing or repairing the transfer case will fix this.

When does this sound happen? Does it do it in 4wd or in 2wd? Does the sound change when turning?
If the t-case is visually not broken, it could be just a strecthed chain inside the t-case. A chain is about 280.00 dollars plus installation

Often this is due to faulty starter motor, or faulty ignition block.