John,
Your coach was one of the first Monaco built Beavers, and Monaco was using Dexron III in all Allison transmissions at that time. However since your coach is over ten years old, it may have already been converted to TranSynd by now. If there are no markings to identify what transmission fluid is in your coach, you can have an oil analysis run on the fluid to determine what fluid is in it now and if service is needed.
Gerald