I have a 2008 M2 business class with a C9 Cat w/425hp. The Allison transmission holds well under load, but doesn't like to shift as the truck begins to move. It likes to hold up in 2-3...3-4...4-5 gear changes. It seems to just linger and no want to shift up unless I back off the throttle. I pull a 53' van for our pulling tractors at about 32k. Is there anyone that can beef up the trans to handle and work well, or do I search for a hd hauler? Thanks!
