I am new to Jeeps and have a 90 XJ with the command track transmission (no fulltime 4wd). The indicator light for the 4wd does not come on when engaging 4wd. With 4wd engaged the it appears that the front wheels are not pulling at all. The transfer case seems to engage properly and there are no unusual noises. The rears will spin and the fronts just sit there. What sort of a problem might I have?