I just found out that I need to replace the right rear frame section on my Pathy, and read some pretty discouraging posts. Then I remembered my dear old Land Rover (SeriesII 88"), and am now determined to save my Pathfinder. I am happy to have found this thread now, as I believe you guys are on the right track here. first of all, let me say that I am not here to shower the Landy with praise, or to put down the Pathy, the Nissan is by far the better on-road vehicle and the rest is like comparing apples to oranges. I will say, however, that Land Rover dealers have a better attitude toward helping their customers with problems. Land Rover dealers know, confess, admit, provide help for, AND MAKE MONEY FROM problems related to the REALLY crappy box frames that they put under their older vehicles. Check out the sites of places like Atlantic British and Rovers North. You can buy any piece of the frame (or a whole new frame {$2000.00}---for an early 1960's vehicle). The attitude is typically British and is this:
"Oh, the rear crossmember has rusted itself to pieces? Well, old boy, modern science HAS found the cause of this malady. You've simply neglected to spray enough no.2 fuel-oil mixed with your used engine oil onto the bloody thing. You ARE changing your oil every 5,000 miles aren't you? well then what are you doing with it, saving it up for your Guy Fawkes bonfire? Anyhow, not to worry, we have a nice new one for you on the shelf. Just cut the old one off and weld the new one on. Use the cab mounts and what's left of the frame as your jig. There's a good chap!"
Nissan dealer's attitude:
"Ah, rusty frame? Yes, frame rusts, so sorry, go away!"
Anyhow, treating the inside of the box frame has been done by Land Rover owners for years. Reading your posts about this gives me new faith, especially now that I am in the Nissan camp. I have used POR 15, I love it, but I think that I will go with the enivironmentally-friendly fish-oil stuff. Reason being that POR-15, while it will be more permanent than oil, does not spead like oil. It only coats the area where you put it. Oil spreads (to some extent, anyhow) to areas that you might not have hit. Landy owners often use the jet nozzles from oil furnaces (get the ones with the biggest orifices and widest spread patterns) on the end of the frame-sprayers. The use of phosphoric acid prior to the rinse-out may get rid of some of the really bad rust, and drying with heated air or with nitrogen (available in cylinders from your local welding supply) between the rinse and the oiling will help.
Thanks all for being here,
Bill