I am looking at buying a 05 ram 1500 that the body is very clean on. I was doing some research and found some cases of the frames rusting through from the inside out on some under the rear doors. Just looking to see if anyone has seen this or how common it is. I tried to measure the thickness of the frame on the one that i am looking at in that area and the best i can come up with is it is .120 thick in that area and when specs are looked up it shows it should be .150-.170?

It must be tough living in an area where you have to be concerned about frame rust on a 10 year old truck. But I remember being in La Porte, IN in Fall of 1977 and seeing a late model Chevy truck with a lot of the bed side gone due to rust. It was even uglier than normal.

Yes it does add dificulty to things. You would be amazed at 4-5 year old cars here with rusty door seams and holes starting in panels.

I know many people still driving Dodge trucks from teh 90's, and there is no frame rot that I heard of. My current 97 Dakota is finally starting to rust, but the frame is not a concern at all.

Now, my name-sake 79 W150 simply broke in half while driving down the road. The frame rotted due to debris loading between the fuel tank and siderail of teh frame, a common problem for that era of truck.

I live in SE WI.

That era of ram I've not heard of frame issues (actually none of the different eras have any frame issues that I've heard of). Rear wheel arches and cab corners for sure, mine are blowing up with cancer as I type. If those are good then I wouldn't have any hesitations

I haven't seen any 05s with a frame rot problem here at my shop yet, and that's saying a lot. If something is consistently rusting out, I often see it very early.

I have seen a few late model trucks (less then 10 years old) with rear frame rot, but, so far, all of those have been backed into water for loading & unloading boat trailers. Seems the GMC & Chevy trucks that do boats have issues with the rear most crossmembers rotting through, especially the round tube above the axle and the crossmember behind that. The boat using Excursions & Explorers rot the side rails out behind the rear axle.
The only consistent frame rot issue I've seen with the Dodges is at the front where the sway bar brackets attach to the frame. Early Dakotas rust through the boxed frame near the trans crossmember, and where the channel is welded to the tube frame, under the cab.
Most frames tend to rot out from the inside out, any boxed tube frame can hold moisture and can rot out. Automotive floor boards also rot out from the inside, 95% of the time. Its caused by water sitting on top of it. That wonderful jute backing on carpet will hold moisture for 2 weeks after it gets wet once! Gene