I bought a 10 year old TJ recently and took the doors off for the first time in her life. It took a lot of effort. The best advice I can pass along is open the doors to about 90 degrees to the body, lift with a steady force, no jerking, and wiggle the doors back and forth as you pull. When they've never been off before, they don't just slide up, it was slow going. Took about 5 minutes of steady force to get each one off, not counting breaks, but slow progress was evident. I've heard of people using a piece of wood placed along the lower sill with a jack under it to lift the doors off, but I was a little hesitant to try this. Turns out it wasn't necessary.