Another post about frame rust

Appears to be an 03-06 manual. That’s fairly good when it comes to rust since

1) 03-06 tends to see less frame problems.
2) you essentially have a drain hole where the automatic transmission cross member should go.

Figuring out frame rust is very very easy on Tj’s. If the inside of the frame is smooth throughout, you’re in a good spot. If the inside is not smooth but has no chunks, you’re starting to see a problem. If you can pull sizable chunks out of the frame (like I could with my old frame), then you should start worrying a lot.

A lot of people forget the outside simply does not matter. The inside is what counts.
 
Appears to be an 03-06 manual. That’s fairly good when it comes to rust since

1) 03-06 tends to see less frame problems.
2) you essentially have a drain hole where the automatic transmission cross member should go.

Figuring out frame rust is very very easy on Tj’s. If the inside of the frame is smooth throughout, you’re in a good spot. If the inside is not smooth but has no chunks, you’re starting to see a problem. If you can pull sizable chunks out of the frame (like I could with my old frame), then you should start worrying a lot.

A lot of people forget the outside simply does not matter. The inside is what counts.

Found all kinds of chunks and goodies inside one side shortly after purchase and I've just been religously FF'ing ever since. Don't think there's much else you can do besides clean it all out as best you can and cover it with some sort of inhibitor. I still can't find any holes or weak spots but I feel like it's only a matter of time given I DD, even on salty winter roads.
 
Really, you drove 20 miles with nothing holding the T case up. That could end up bad. While your working on your frame rust put a floor jack or jack stand under the Tcase. Get a good look inside your frame and see if your rotting from inside out. Then if the frame looks ok, clean it and paint/treat the frame. Before you drive again, put the skid plate back so the drive train doesn't drop out. Best of Luck.
 
It sorta looks like some of the scary rust could be from the skid itself. And rust on the exhaust and driveshafts is pretty much inevitable and not that serious. Until the muffler falls off that is.

But for God's sake always support the trans. If the skid is off then a jack needs to be holding the trans up first. There was a mount bolted to the skid when you took it off, wasn't there? Snap a pic of that too.
 
Put the skid plate back on and the Jeep seems to be running fine. I’ve accepted the fact that I may have ruined my motor mounts and u joint and will likely have to pay some money to fix them. Sounds like the transmission and transfer case likely aren’t harmed, so it is what it is.

Back to the rust. Finally took a hammer to it. Some shucks definitely popped off, but nothing that seemed like it was going to break through. Here’s some pictures after the hammering.

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I suspect that your looking a rust from trapped moisture between the frame and skid rather then frame inside out. Get an angle grinder equipped with a wire knot brush and give it a thorough cleaning and coating. Something like POR would be a good treatment. I like to add a fat washer between the skid and frame to provide additional clearance so it will stop trapping moisture.
 
Put the skid plate back on and the Jeep seems to be running fine. I’ve accepted the fact that I may have ruined my motor mounts and u joint and will likely have to pay some money to fix them. Sounds like the transmission and transfer case likely aren’t harmed, so it is what it is.

If it drives ok I doubt that you have damaged anything.
 
I suspect that your looking a rust from trapped moisture between the frame and skid rather then frame inside out. Get an angle grinder equipped with a wire knot brush and give it a thorough cleaning and coating. Something like POR would be a good treatment. I like to add a fat washer between the skid and frame to provide additional clearance so it will stop trapping moisture.

Dumb question but you'd use a grade 8 metal washer yeah? Instead of nylon or something (not sure if strong enough for this application) - guess I'd just apply liberal amounts of FF
 
I now have a Barnes skid plate that is flat where it mounts to the frame. Because it is flat the nutserts provide some clearance to the frame so it doesn’t trap water. The OEM skid plate had no clearance and I was getting some frame rust due to trapped water.
 
Just use any old washer that is metal between the skid and rail. As said, get an angle grinder with a good wire wheel and get as much rust off of the frame (actually everywhere) and use a good primer and paint. If it is Spring where you are then the sooner the better. If you are still getting nights in the 40's and low 50's you might want to wait or have a heated garage so the prime/paint can cure properly. Find a post about drilling drain holes in the frame and do it. Then a good coat of fluid Film or cosmoline can hold the rust in check. Before you do that try and get as much work that needs to be done underneath first. It will be easier to work on the Jeep without the waxy and greasy sprays.