Dad also removed the water tank from its location, under the rear bed. This is a huge plastic tank that's sitting right on the plywood floor. Dad wanted to make sure that the plywood floor under the tank is not rotten. It turned out that the plywood is in perfect shape.
Meanwhile Dad drained the auto transmission and dropped the pan in order to inspect the filter. A lot of sludge in the pan and a dirty filter are usually signs of something wrong with the tranny. However the pan only had a very small amount of sludge and the filter looked quite clean, wich is good considering the mileage of the vehicle. The transmission will get some new fluid, and since it shifted very well on the road no problems are expected with the transmission.
Today Dad removed the front wheel hubs to inspect the wheel bearings. Everything is in perfect condition. These are very strong heavy-duty truck drivetrain components, and it's still like new.
