1997 ford explorer 4x4

1997 ford explorer is engaged in 4 wheel drive but there are no indicator lights on.my question is ,is the motor bad?when i pull the motor the transfer case shows it is in 4 wheel drive,if i manually try to shift the transfer case the linkage is like it is spring loaded and stays in 4 wheel drive .does the motor hold it in 4x4 untill the wheels slip and then move to 4x4 for that brief time that the wheels are slipping? any help!!!thanks