My son recently bought an older Chevy p/u with the fuel efficient 8.1 and Allison trans. Has about 150k miles. He doesn't know the service history on the trans but wondered if it should be serviced. Our experience with conventional trans has been if it hasn't been serviced ever or in a long time and then do a fluid and filter change, it's a death sentence for the trans. Is the same true with the allisons? Should we service it? Or.... if it works- don't mess with it? Thanks