My 04 disco feels like only the front wheels are pulling. The front tires also look to be wearing more than the back. I remember that there was a way to disable the rear shaft and only pull from front if there were issues with the rear shaft. Where doni check to see if the rear is disengaged?

 

incorrect.

pull the front shaft. engage the cdl and try and drive.

 

For the rear to be disengaged, you would have to remove the rear drive shaft. Look underneath and look for a round shaft going from the center of the truck back to the rear axle.

 

You have no knowledge about your Disco and the drive train.
How often do you rotate tires, what air pressure are you running front and rear and if you slowly turn a full turn circle in a parking lot, do you hear the front tires chirping?