Double frame and rust between frame rails

That's incredible. I didn't realize it was rust jacking. At first I thought it was a plate in between the rails.

 

It's unreal the power of rust jacking. We've got an old tanker that has sat for 20 years. There must be places the steel has spread a couple inches

 

I've never seen it so bad before....crazy. I try my best to keep my frame and anything it touches coated with something. I've been using BLO/WD40 on everything lately and it's quite impressive.

Not much can be done to stop sweating in between layers of metal but I think the OP might be on to something if his idea can actually get a fluid between the rails.

 

My 1980 had an insert along where the suspension bolted up. Rust spread the two lower flanges an easy 2 inches apart.

 

3/8 or 1/2” single rail is the way to go in salt, we did rails on a dump truck but sold the last double frame tractor to not have o deal with it again, there is no stopping it, just replacement

 

lf you look close you can see how the frame rails are opening up and tilting the fifth wheel slides etc. Plus the suspension hangers on the Pete seem to collect water and rot out the frame rails too

 

Not to sound like I am picking on anyone, but steam cleaning chassis and washing truck regularly saves a lot issues from happening.

 

Every weekend. 5+ years running salt and nothing but surface rust.

 

Double framed trucks up here do ok until they get around 15 years old. By 20 it's rare but to have those issues. Not saying you can't find ones that aren't in really good condition. But in everyday work trucks it's hard to find one that 20 years old without similar issues.