My old 73 Ford pickup had the same problem. Turned out that the durometer of the rubber in the twin I-beam suspension was too soft which allowed the shimmy. Occurred at 65mph after going over railroad tracks every time. I fixed by adding a shock absorber device off a Blazer to the steering rods. Ford fixed by making the rubber harder. Ford never acknowledged the problem and lied to me at the dealer about it. I learned what I have said from Smoky Yunick's Popular Science column. Could there be some rubber parts in the front suspension of the RAM causing this? I'am interested as I have a 2005 RAM Quad Hemi 4X4. Have never had this happen but since yours started doing this at 115,000 sounds like deteriorated parts. Others should have run into this unless the part causing it was limited to one supplier which is possible. Check with insurance companies or the NTSC. They may have heard something. I suspect that Chrysler will stonewall you and not provide any info. Good luck.