Looking at a Dodge service truck with cummins and a 4 speed auto transmission. Have all the service records from new. Tranny replaced once. Now has about 190,000. No other major repairs done. Will this truck pull double NH3 tanks? Do they have a 4wd low speed? Truck is 300 miles away. Son is able to bid on it thru his workplace. Our main concern is with the auto tranny. Any thoughts?