Gary,
With proper maintenance you Allison is not even half way through it's life expectancy. The only thing that is a negative for it is it's age, because the seals can fail from age as well as usage. Just remember that your transmission was designed for a truck were the 140K that your coach has, is only a year of use or less. So the miles on your transmission are not a real concern with proper fluid and filter changes if you watch out for any leaks that might develop.
If your dipstick is not marked that you are running Transynd the only sure way to tell is to see if your local Allison dealer can run a fluid analysis to check fluid condition. This will tell you the type of fluid you are running, as well as give you a little insight into the condition of your transmission.
Gerald