I have heard spray the frame with WD40 (helps break down rust and protect frame by dispersing water) and I have heard dont spray (promotes rust and removes paint) … thoughts and suggestions?
I would not worry about it with a JK. YJ’s and earlier TJ’s did not have the frame rust treatments that newer vehicles have.
Just rinse the undercarriage after driving salted roads.
Spray it with fluid film. It can be had from 15oz rattle can to 55 gal drum. I was researching products this past winter to use on my snow plow and found this…works great
one customer of ours swore up ad down that putting atf inside his frame would keep it from rotting. He had a VERY clean TJ (lifted big tires ect) the frame was perfect no rust at all. Well last winter he went to make a left hand turn the both rear lower control arms ripped off the frame…Upron inspection there was a ton of rott inside only in that one spot. The only thing i can think of is that the atf wore the paint and metal down enough on the inside to make it rot at an exsessive rate. Wierdest thing i ever saw. The atf literally pooled up where the mounts ripped off.
I’m with Eric, in that you shouldn’t need to coat the inside of a frame on a JK.
That said, I have been using linseed oil on the inside of my frame for a number of years.