Toyota Repair: 1990 4runner stuck in 4L but shifter moves freely, shift linkage, shift forks

Question
I am working on a 1990 4runner 3.0 auto 4wd,227k, for a
coworker.He just bought it and it is stuck in 4L.I have no idea
about this trucks repair history but whoever he bought it from
was a hack. i jacked the entire truck in the air and only the rear
wheels turn the front driveshaft turns but not the wheels and
there is no 4wd light lit on the dash.I looked over the transfer
shift linkage and it moves freely to all selectable positions but
dosent actuate anything just stays in 4L. i read in some of your
other responses about the actuator on the front axle and i will
look into that for the front wheel problem but for the shifter
issue i noticed a second oil pan on the trans/transfer case above
the crossmember. The transfer case linkage selector shaft  goes
into the case just above this pan on the drivers side. If i pull this
pan down will i be able to see the selector on the inside and tell
if something is broken or dissconnected (shift fork or actuator
rods).All in need to do is get the case back into 2H my coworker
dosent care if the 4wd works or not at this time. thank you in
advance for your help.

Answer
This transfer case is controlled hydraulically there are no shift forks, the only thing you will find in the small oil pan is a valve body that controls the transer case by putting it in either HI or LO 4 by applying clutches and utilizing a planetary gear to provide the two speeds.
It sounds like there is a serious problem with the transfer case and it may have to be replaced.