Blackwater
Engineering Geinus
If there is nothing wrong with the transmission then just do a oil and filter change. its recommended to change it every 1000,000 miles.Preventively I would consider having the transmission overhauled. Mine crapped out while in town and would not go very far before it stopped working. And since you are looking to do hauling and trips I would look to having this done. Towing fees and inconveniences suck on the road between major cities. And possibly look at having shift kits or HD build done now.