We have changed filters every 75000 and dropped fluid every 150000 using syn Transynd that Allison recommends. Last shop said due to our current business model we could just change fluid and filters every 150000 miles. We only use Allison shops. Be careful some say they can service but they are not authorized Allison repair shop.
I have a Allison Auto. I change filters every 50-60K. I change the fluid only because I didn't know the last time it was done. But with the Transyad. They say every 500K.