[reisser]

Get creative. Force air through your lips and teeth at a high pressure. There is your pneumatic sound. Run a motor and record that in a secluded area... slide two pieces of metal together... anything that sounds remotely mechanical and you have your forklift. Don't sweat not having the real sound. These kinds of sounds should fit quite nicely. Plus, you can customize them to fit your animation.

Just a suggestion. Good luck.