Please forgive me, if this is a dumb ? Or it has been asked more times than it needs to be. But have not find it searching.
To start off, I have a 2005 Chevy Kodiak C5500. That had a 2000 5.9 24 valve RV motor hooked up to a 5 speed Allison 5.13 rearend on 225/70R-19.5 tires and wheels. The trans has the Sun Coast 6th gear kit added to it. Pulling 16,000 lb 41ft long 13.3" tall 5th wheel camper. It does a good job, but does not down shift until 40 MPH. When your pulling a big hill, it does pull good. But it needs to down shift at a higher speed. Or feels like it to me. As by the time your down to 40 MPH. And it drops to I sure its 4th gear rather then 5th. Is this normal or just a bad tune that has been running for 35,000 miles?
The trans has a stand alone box for it and EFI live tune. If anyone is in West Tn Middle Tn North ms or North Al and can tune these. Please let me know and would love to get it turned where it down shifts into 5th gear to help out pulling.
Pete